9851 6283 01b Rock Reinforcement complete.pdf

Rock & Soil Reinforcement

third edition

www.rockreinforcement.com

Talking TechnicallyCase Studies

Product Specifi cations

a technical reference edition

Atlas C

op

coR

ock &

So

il Rein

forcem

ent

Th

ird E

ditio

n

The

face

of

inno

vatio

n

Supporting your business wherever you are

Atlas Copco MAIPhone: +43 4245 65 16 60 Fax: +43 4245 65 16 68 00

Atlas Copco supplies the widest range of advance cost-effi cient rock reinforcement solutions for mining and tunnelling, including fully-mechanized Boltec rock bolting rigs, Swellex rockbolts, and MAI self-drilling anchors.Each and every product has been designed to help maximize your tunnel advance and minimize costs per drilled metre – and always with the highest level of safety in mind.

Because we’re a global organization, we have the resources to be truly local. Find out more at www.atlascopco.com and select “Country”. Or give us a call. We’d be happy to listen to your requirements, and even happier to meet them.

www.atlascopco.com

Printed matter no. 9851 6283 01b

Foreword2 Foreword by Federico Scolari, Vice President Marketing,

Atlas Copco Craelius.

Talking Technically3 Innovative Solutions for Rock & Soil Reinforcement5 Investing in Rock Reinforcement7 Controllable Rock Reinforcement

11 Swellex Manganese Offers Improved Work Index13 Swellex Premium Line15 Hollow-Core SDA System17 Atlas Copco MAI Self Drilling Anchors19 Symmetrix For Large Holes22 Sacrificial Drill Bits24 Mechanized Bolting28 Using Rocket Boomers to Install Rockbolts33 Connectable Swellex35 Rockbolt Corrosion in Mining and Tunnelling38 Grouting for Support in Tunnels41 Rock Mass Stability with Swellex43 Secoroc Uppercut – New Tapered Equipment 45 Getting the Drift with Magnum SR47 Rock Mechanics and Rock Reinforcement51 Swellex in Shear Stress55 Using ROC Drillrigs to Install SDA59 3-D Imaging for Rock Support Design 61 Introducing Swellex Hybrid

Case Studies 63 Swellex in Mining: project reports from Canada,

Portugal, Turkey and Peru.69 Removing Bottlenecks in Austria: upgrading the

European highway system in Central Europe.73 Extreme Temperatures: rock reinforcement in

permafrost in Northern Quebec and volcanic strata inHokkaido.

75 Coated Swellex at Kvarntorp: longlife installation ofrockbolts in a corrosive environment.

77 Nuclear Quality Assurance: long-term tunnel supportfor the Exploratory Studies Facility at Yucca Mountain, US.

81 Versatility in Tunnelling: project reports from China,Germany, Madeira, Spain, and Switzerland.

87 Rapid Support Close to the Face: reporting use ofSwellex at three important Italian TBM tunnelling sites.

91 Large Hydroelectric Projects: widely differing demandsat sites in Austria, Bhutan, India, Philippines and Portugal.

97 Top Combinations in Japan: reliable support insedimentary and volcanic rock formations in railway androad tunnels.

99 Front Stabilization Using MAI Rock Anchors: pre-reinforcement as a means of ground control inGermany, Italy and Taiwan.

104 Boltec at Kemi Mine: integrated process controldemands reliable and consistent mechanizedrockbolting.

109 Overcoming Squeezing Ground at Mitholz:supporting deformed strata while fresh support isinstalled.

113 Mechanized Bolting at Zinkgruvan: better rockreinforcement improves production and safety.

115 Seismic Tunnelling at Bolu: crucial motorway tunnelsrecover from earthquake using Self Drilling Anchors.

119 SDA in the Baltic States: novel uses for grouted SDAas micropiles to support ancient buildings.

124 Increasing Land Use: SDA applied to subsoilstabilization prior to housebuilding in UK.

127 Soil Nailing UK Transport Routes: securing majorroad and rail infrastructure using SDA.

129 Portal Support Using Swellex: stabilization ofentrances to Porte tunnel in Italy.

131 Driving From Budapest to Nürnberg: difficult tunnelsusing advanced rock reinforcement techniques.

135 Systematic Grouting at Oslo Subway: CraeliusUnigrout provides the perfect solution for water ingress.

Product Specifications139 Swellex Manganese Line 144 Plasticoated Swellex 145 Swellex Premium Line148 Swellex Hybrid149 Swellex Face Plates & Washers150 Swellex Pumps152 MAI SDA164 Tophammer Crawlers166 Boltec Rigs172 Rocket Boomer Drillrigs174 Hydraulic MAI Bolt Support175 Hydraulic Rock Drills 178 Hydraulic Feeds180 Symmetrix Overburden Casing System188 Unigrout Grout Plant189 Pusherleg Drills190 Secoroc Threaded Equipment204 Secoroc Tapered Equipment

Front cover: Different applications involving rock reinforcement. Atlas Copco reserves the right to alter its specifications at anytime. For latest updates contact our local Customer Centers orrefer to www.rockreinforcement.com

ROCK & SOIL REINFORCEMENT 1

Contents

Produced by tunnelbuilder ltd for Atlas Copco Rock Drills AB, SE-701 91 Orebro, Sweden, tel +46 19 670-7000, fax -7393.Publisher Ulf Linder [email protected] Editor Mike Smith [email protected] Picture Editor Jan [email protected] Contributors Anders Arvidsson, Claes Hillblom, Federico Scolari, Francois Charette, GunnarNord, Hans Fernberg, Juha Hyvaoja, Jukka Ahonen, Lorne Herron, Mario Bureau, Mark Bernthaler, Olle Karlsson, Per-OlofEinarsson, Sara Sjödin, Sten-Ake Peterson, all [email protected]. Adriana Potts, [email protected] Jones, maurice@tunnelbuilder. com. Wulf Schubert, Markus Potsch, Andreas Gaich, all [email protected].

Designed and typeset by Sheldon Mann, Belvedere, Kent, UK

Printed by db grafiska, Örebro, Sweden Copies of all reference editions are available in CD-ROM formatfrom the publisher, address above. Reproduction of individual

RR3 CONT.qxd 19/7/05 8:33 Page 1

2 ROCK & SOIL REINFORCEMENT

Foreword

Ongoing development of faster, safer and more exotic tunnelling techniques places a con-stant pressure on manufacturers to provide more efficient rock support solutions whichwill help the shortening cycle time.

The use of versatile drilling jumbos for mechanized installation of a variety of rock supportsystems is part of the leading practice used in modern tunnelling. As ground conditions get moreand more demanding, emphasis is placed on flexible and intelligent support systems in which rockand soil reinforcement is expected to contribute to the productivity and safety of the operation.

The trend has been to provide rock support/reinforcement systems that are easy to install, assureefficiency and provide safety, both during and after excavation.

For the last 25 years, Atlas Copco has been offering the Swellex concept as a unique, safe andreliable system of rock support. As the market leader in underground rock excavation technology,Atlas Copco has also been developing safer and more efficient rock reinforcement products suchas the Manganese Line rock bolts, which are manufactured from a special type of steel. Anotherdevelopment is the Swellex Premium Line of rock bolts, for use where high yield load and stiff-ness are expected from the reinforcement system. The recent acquisitions of MAI and Rotex haveintroduced a whole new range of products, which are now being developed for mechanized instal-lation by both surface and underground drillrigs, creating fresh applications in rock and soil rein-forcement.

Atlas Copco’s Rock Reinforcement Competence Centre at Feistritz/Drau, Austria brings togeth-er the skills necessary for the development of superior rock reinforcement products to serve thetunnelling, mining and construction industries worldwide. In 2005, the centre became a part ofAtlas Copco Craelius, which is active in ground engineering with Symmetrix and ODEX overbur-den casing drilling systems, and Unigrout and Logac grouting equipment, and produces multipur-pose drilling rigs such as the Mustang. The combined product portfolio includes Swellex and MAI,bringing together all elements of the Atlas Copco rock and soil reinforcement strategy.

As a result, market-driven product development at this new facility is already setting the scenefor another quarter-century of development in rock reinforcement and ground engineering.

Federico ScolariVice President MarketingAtlas Copco Craelius

[email protected]

RR3/FORE.qxd 19/7/05 8:36 Page 2

Leading the Way

When Atlas Copco applied for patentsfor the Swellex rock bolt in 1979, itwas a significant milestone in rockreinforcement technology. This inflat-able bolt was extremely easy andquick to install in a 38 mm hole, andprovided immediate support.

The advantages proved to be soeffective that over the next decadeseveral million Swellex bolts wereused in demanding ground conditionsworldwide.

In the years that followed, this suc-cess led to the development of severalnew versions including:

• Coated Swellex with rust protec-tion to withstand corrosive environ-ments

• Super Swellex for larger holediameters and a 20-tonne load-bearingcapacity

• Connectable Swellex for tunnelswhere the length of the bolt required ismore than the height of the tunnel

• Swellex Hanger for suspendingsuch facilities as conveyor belts andworking platforms

• Swellex Manganese for increasedtensile strength and higher elongationcapacity

• Swellex Premium Line forimproved yield characteristics and ten-sile strength with slightly less elonga-tion.

Specialized Rigs

At the same time as applying forpatents for Swellex, Atlas Copco

launched the Boltec 500, a new rig forfully mechanized rock bolting, primar-ily to increase productivity and toimprove safety when installing thebolts. Safety is an especially importantconsideration on sites with poor rockconditions.

However, the extreme conditions ofrock bolting, in which water and rock

TALKING TECHNICALLY


Innovative Solutions for Rock andSoil ReinforcementTwenty Five Years OnOver the past 25 years, AtlasCopco has developed a constantstream of products that have pro-vided innovative solutions to amultitude of rock support andreinforcement tasks, and solvedmany difficult challenges forminers and drilling contractorsaround the globe.

Further developments are onthe way with the recent inaugu-ration of a dedicated competenceand R&D centre for rock rein-forcement in Feistritz/Drau,Austria. Located at the headquar-ters of Atlas Copco MAI, thecentre is dedicated to developingcutting-edge products for rockreinforcement and ground engi-neering applications. Official opening of the new Atlas Copco rock and soil reinforcement competence centre at Feistritz/Drau,

Austria.

Atlas Copco Boltec LC is a highly productivemachine developed specifically for rock bolting.

RR3/RT1 24/6/05 17:01 Page 3

cuttings pour down along the drillstring and onto the rock drill, feed andmoving components, had a negativeeffect on the service life of these rigs.Their performance was affected evenmore when cement-grouted bolts wereused, due to cement spilling out of thehole onto the bolting unit.

In response to these challenges,Atlas Copco continued to develop fur-ther generations of more rugged andreliable bolting rigs that had fewermoving parts.

The current fourth generation rigs arecapable of impressive performances. Forexample, the Boltec LC working in aFinnish mine recently installed morethan 120 Swellex Manganese bolts in asingle 8-hour shift.

Boomer face drilling rigs also beganto be used for tunnelling in poorground, drilling holes for rock bolts aswell as for the installation of pipe roof-ing systems and self-drilling anchors.

Swellex Still Supreme

As the Swellex patents have begun toexpire, other producers have maderepeated attempts to imitate the designand features of the Swellex bolts, butnone have managed to achieve thesame quality.

Swellex remains supreme, and AtlasCopco remains firmly at the forefront of

this technology, continually setting newstandards and breaking new ground.

In 2002, the company added self -drilling anchors (SDAs) to its everwidening product range, through theacquisition of SDA specialist MAIAnkertechnik of Austria.

These fully-threaded anchors, fittedwith sacrificial drill bits, are designedfor exceptionally poor ground condi-tions where holes collapse and con-ventional bolts cannot be used. Inaddition, they are used in combinationwith crawler drillrigs for surface appli-cations, such as soil nailing in slope

stabilization, and in ground engineer-ing for foundation reinforcement.

Atlas Copco MAI SDA are nowcommonly used with modifiedBoomer drill rigs. In this case, the drillrod and bit are replaced by an MAIadapter, coupling, anchor rod and asacrificial drill bit.

Competence Centre

The recent opening of the dedicatedcompetence centre at Feistritz/Drau,Austria heralds a new era for thedevelopment of superior rock rein-forcement products to serve tun-nelling, mining and constructionindustries worldwide.

A considerable amount of market-driven product development will nowbe possible, and customers around theworld can expect to see many new andinteresting products in this areacoming from Atlas Copco in the yearsahead.

The scene is now set for anotherquarter-century of development inrock reinforcement and ground engi-neering.

On the following pages, Atlas Copcopresents some technical papers, casestudies and product specifications todemonstrate this technology in action.

by Federico Scolari

TALKING TECHNICALLY


Innovative two boom cable bolting rig drills with one boom while feeding and grouting cable with the other.

Twenty five years of innovative solutions to rockreinforcement problems.

RR3/RT1 24/6/05 17:02 Page 4

Practical Solutions

At Atlas Copco, as a supplier of rockdrilling equipment as well as rockreinforcement tools and material, thereis an ongoing drive to create new orimproved solutions to rock reinforce-ment problems. This topic is generallybroached at an early stage of a projectby the contractors, and is brought upconstantly by the mining industry. Asa result, Atlas Copco is right at thecore of practical solutions for rockreinforcement, and this has con-tributed to our approach.

The Atlas Copco focus is on totaleconomy, by fast installation of rocksupport, adequately proven perfor-mance of reinforcement, and a tech-nology that has the capacity to meetmodern quality demands.

In this presentation of the AtlasCopco approach, we discuss the costimplications of the time taken for theround in tunnel excavation, the qualityof the Atlas Copco rock reinforcementprogramme, and working environmentand safety aspects.

Improving Performance

Going back 20 years or so, and look-ing into the time needed to excavate around and how this has developed,will indicate the direction in whichtunnelling technology is going. The round cycle is just as real today as it was then. By doubling the effort, the time taken will reduce by50%.

In a linear situation, for instance, ifit takes 100 days for one man to dig adefined dyke, 100 men can do it in oneday. In tunnelling, life is not that easy.There may be only one face to workat, and there is usually little space forincreased efforts at that face. The onlyremaining option for the tunnellers isto improve mechanization.

The leading process has beendrilling at the face. Since the introduc-tion of the original Swedish Method,the drilling performance has improveddramatically. The introduction ofheavy pneumatic drifters mounted onarticulated booms, followed by threegenerations of hydraulic drill rigs, hasfurther multiplied productivity.

If we consider a tunnel with 80 sq mcross-section being driven in fracturedlimestone with clays strata, through a couple of major faults, and with350 m overburden and significantwater inflow, the drilling phase hasdecreased from 40% of the total

TALKING TECHNICALLY


The latest Atlas Copco Boltec offers a new dimension in rockbolting safety.

Investing in RockReinforcementSafety and EconomyTime was, in tunnelling andmining, that rock reinforcementwas considered a burden, a cost,and a necessary pain. The aimseemed to be to get around thesupport work in the easiest andcheapest way possible, and con-centrate all efforts on excavatingthe greatest amount of rock, inthe shortest time.

As the awareness of the con-sequences of poor rock reinforce-ment becomes more widespreadamongst clients, engineers,miners and contractors aroundthe world, a sounder attitude tothis work is emerging. There isnow a wish to achieve therequired demands on quality, tocarry out the support and rockreinforcement in the right order,to properly monitor what hasbeen carried out, and to evaluatethe results of the rock reinforce-ment effort.

As contractors and miners havea reputation for looking after theirmoney, new ideas are born onhow to carry out the support andreinforcement work in cost effi-cient ways, and they are often pre-sented as alternatives in theirquotations on underground con-struction projects. In mining, thereis continuous ongoing evaluationaimed at optimization of the exca-vation reinforcement method.

RR3/RT2.qxd 24/6/05 14:54 Page 5

drilling time 20 years ago, to just 20%today.

Figure 1 illustrates the developmentof drilling and ancillary face opera-tions over 25 years. Not all the differ-ent phases in the cycle have the samedevelopment. Shotcreting shows apositive trend on time reduction, whilemucking has a less noticeable devel-opment. These figures would improvefor a smaller cross section. Scalingshows a large increase in time, sinceheavy hydraulic breakers now play animportant role in improving the pull ofthe blasted round by cleaning off theface, as well as trimming the profile ofroof and sides to make safe.

If we consider traditional, fullygrouted rockbolts, installed with ajumbo or with an automatic bolting rig,the increase in productivity does notkeep pace with the drilling. In our ref-erence tunnel we can register a poorsaving of 10% in total time consump-tion. Rock reinforcement, and in par-ticular, rockbolting, is a bottleneck inthe excavation cycle, and this has to betackled in order to boost productivity.

Time is Money

In tunnelling the time related cost is mostlikely in the range of 50- 60% of the totalcost. This means that, if no work is car-ried out during the set construction time,

with all resources mobilized and the stafftaking home their salaries, the cost willbe at least half of the forecast cost.Conversely, if the work is carried out inhalf of the set time, the reduction in costwill be at least 25%.

Assume a tunnel of 1.2 km inlength, with a cross-section of 70 sq m,will be excavated over a time period ofone year. This is an average advance of100 m/month, at an estimated cost of€5,000/m or €6 million in total. Thetime related cost will then be at least€3 million, or €2,500/m. If a reductionin construction time of one month canbe achieved, it results in a reductionof the cost by €250,000. Further,assuming that the working time is500 hours/month, then the cost saving

will be €500/h saved. Consequently,there is a good incentive for lookingfor cost saving measures, and rock rein-forcement certainly is an area of interest.

Atlas Copco has taken this problemseriously. Our approach is to providemachines, rockbolts and know-how toadd value to your rock reinforcement.We hope that the articles in thisbrochure can explain how.

Investing in RockReinforcementThe Atlas Copco commitment istowards a safer and more ergonomicworking environment. This commitmentis translated into ergonomic machinesand reliable rockbolts. There are noshortcuts in this process. Swellex offersimmediate support, with full columncontact, and pumps check the inflationpressure of the bolts. Self DrillingAnchors (SDA) are replacing manualinstallation of rockbolts in collapsingholes, where the manual job is more dif-ficult. Boltec offers a new dimension inrockbolting safety, while Cabletec doesthe same for cable bolting.

Assuming that you have doneeverything to optimize your facedrilling, and that your detonators andexplosives are the best available. Youhave a modern ventilation system, themost powerful mucking equipment,and the most efficient shotcrete robot.And you still stay with the mostconventional rockbolting system?

Then it’s time to invest in rockreinforcement.

by Gunnar Nord

TALKING TECHNICALLY


Figure 1. Development of face excavation over the last 25 years, showing the changes in time taken forvarious components of the round.

Rocket Boomer L1 C-DH drilling rockbolt holes at Auersmacher in Germany.

RR3/RT2.qxd 24/6/05 14:54 Page 6

Controllability Means SafetyTraditionally, the use of rockbolts hasbeen limited to reinforcing reasonablysolid rock. Poorly consolidated andfriable rock conditions have requiredthe use of expensive external support.

Independent surveys reveal that asmany as 50% of cement- and resin-grouted rockbolts are so poorlyinstalled that they are virtually non-

functional. The basic underlying fac-tors are: the inherent sensitivity ofresin to heat, age and improper stor-age; parameters during installation;hole annulus; cartridge damage duringinsertion; injection nozzle alignment;presence of cracks and flowing water;and levels of operator skill and care.

This is a highly unsatisfactory resultin terms of worksite safety, and isequally unfavourable in terms of econ-omy. Split-set type bolts may be quickto install, but their anchorage capacityis too low to keep stress concentrationat distance from the rock face.

By contrast, the Swellex conceptentails that the rock is secured by

immediate and full support actionfrom the Swellex bolts. The momentthe Swellex bolt is expanded in thehole, it interacts with the rock to main-tain its integrity. The quality of thebolt installation is automatically con-firmed when the pump stops, and isindependent of rock mass conditionsor operator experience.

Controllability means safety.Control brings peace of mind at everystep:

1) Swellex bolts are manufacturedfollowing a very strict qualitycontrol procedure using specificsteels for which origin and com-position are known and controlled.

TALKING TECHNICALLY


Controllable RockReinforcementHelping Rock toSupport ItselfModern computer-based geot-echnical monitoring techniquesindicate that the greatest relax-ation or movement of the rockmass occurs immediately follow-ing excavation. They confirmthat, after a certain period, therock will establish a new equilib-rium based on its own inherentself-supporting capacity. The bestquality rock will remain self-sup-porting for extensive periods oftime without the need for extrasupport. As the rock qualitydeclines, support requirementsincrease proportionally. The poorerthe quality of the rock, the greaterthe degree of support required,and it becomes increasingly crucialto install reinforcement as quicklyand as close to the face as possibleafter excavation.

Engineers involved in thedesign of rock reinforcement sys-tems must satisfy ever increasingdemands to optimize the designto gain maximum safety andeconomy. The primary objectivein the design of the supportsystem is to assist the rock massto support itself. Accordingly,quality and time are the twomain parameters which must betaken into account when deter-mining the type of rockbolt to beused for rock reinforcement, inboth mining and constructionapplications.

Sequence of installation of a Swellex bolt.

High pressure water expands the Swellex bolt into contact with the strata.

RR3/RT3 11/8/05 15:32 Page 7

TALKING TECHNICALLY


All the manufacturing parametersare filed and linked to a numberon the Swellex bolt bushing fortraceability.

2) Installation of Swellex bolts iscontrolled by sturdy Atlas Copcopumps to assure a perfect installa-tion. The new patented HC1pump, once started, will only stopwhen the set pressure is reached,independently of the operator.

3) Pull-tests can be performed at anytime on Swellex bolts. Whetherthey were installed a year ago in acorrosive environment, or 10years ago in a dry area, it is possi-ble to control their load bearingand yielding capacity. Expertisehas also been developed for exam-ining the bolts with a fibre opticcamera to control internal corro-sion or shearing.

The Swellex concept is designed tooptimize the effectiveness of eachbolt, so the bolting operation matchesthe required safety levels as plannedby the engineers. Alternatively, com-pared to other rock support, the samebolting effort using the Swellexsystem can result in increased safety,since each installed Swellex bolt pro-vides full support.

Swellex rockbolts have been usedsuccessfully to complete many tunnelsin difficult rock conditions while, atthe same time, greatly reducing sup-port costs.

Swellex rockbolts reinforce andimprove the condition of the interfac-ing rock, increasing its load-bearingcapacity.

Depending on the rock massstrength, the pressure exerted duringinstallation may compact the rock sur-rounding the borehole, increasing thefriction along the bolt, and/or deformits profile to match the irregularities ofthe rock, providing a combination ofstrong mechanical interlocking andhigh friction. The resulting highanchorage capacity makes Swellexbolts an integral part of the supporting

arch or beam. Reinforcement is unaf-fected by the presence of water, orjoints in the rock mass.

Swellex rockbolts, and the qualityassured installation procedure, permitrock reinforcement where expensiveexternal support is normally required.

Immediate Support

Modern drilling and excavation equip-ment used in civil engineering andmining applications has led to majorincreases in efficiency and productivi-ty. In fact, development has been sorapid that conventional rockboltingmethods frequently act as productionbottlenecks.

Developments in the speed andease with which rock reinforcementcan be applied to improve equipmentutilization, limit machine downtime,and increase productivity, while simul-taneously complying with safetyrequirements, is of interest to all thoseinvolved in tunnelling and mining.

The Swellex concept has kept pacewith these advances, with a singleoperator installing 50 to 100bolts/shift.

Timing of the rock reinforcementmeasures is of particular importance inNATM, the New Austrian TunnellingMethod. In brief, NATM can beexpressed as a sequence of activitiesfor tunnel development: drilling and

Plasticoated Swellex with cap and without cap.

Mn24H hanger rockbolts for suspending utilities while reinforcing the rock.

RR3/RT3 11/8/05 15:33 Page 8

blasting; mucking and scaling; andimmediate initial rock mass support bysystematic rockbolting and shotcret-ing.

The initial support system restrictsground movements after excavation,thereby maintaining the inherentstrength of the rock mass. This is theessential idea behind NATM. The per-manent lining is installed when therock has reached a state of equilibri-um, and deformation has ceased.

Swellex rockbolts provide immedi-ate support, as well as the ability toaccommodate large ground move-ments at maximum load-bearingcapacity. Shear tests performed byseveral international institutes haveshown that, depending on rock com-pressive strength, Swellex bolts canaccommodate up to 90-100% of theirtensile strength under shear loading,an exceptionally high figure. Jointshear displacement at bolt failure canbe up to 35 mm/56 mm at a 90 degreeangle between the bolt and the surfaceof the joint, showing that Swellexbolts accommodate the same amountof shear displacement as the diameterof the drill hole, and even more insofter rock.

The Right Protection

When it comes to choosing the rightproduct for longevity, or for use in acorrosive environment, it is advisableto proceed with caution. There aremany products that offer what appearsto be lifetime protection.Unfortunately, in reality, the rock massproperties such as water, joints, rockmovement, may be unknown, and thequality of rockbolt installation may beunquantifiable.

Conventional types of rockboltsmade from carbon steel are susceptibleto corrosion. As only 50-70% of resincoated and grouted bolts are properlyinstalled, they do not represent a reli-able solution against corrosion. Also,there is extra delay and cost associatedwith these bolts, compared to theSwellex solution.

To help choose the right alternative,Atlas Copco is using reputable corro-sion institutes around the world toassess the corrosion potential of

ground water around the rockbolt andinflation water within the rockbolt.

It has been established that, formedium term corrosion protection, thebitumen coating is best. However,plasticoated Swellex offers longtermcorrosion protection, independently ofthe rock mass parameter.

If shotcrete or sealant are used, thethreat from atmospheric corrosiondiminishes. In the case of Swellex, itwill seal and protect the inside of thebolt, leaving a reduced corrosionpotential to the external side only. Ifthere is no shotcrete or sealant appliedafter bolt installation, caps can be usedto seal the bolt internally.

A real level of safety is achievedwith Swellex, as the corrosion isassessed, and the bolt can be con-trolled using pull test or internal visualinspection over time.

Total System Approach

The cost and time involved in rockreinforcement compels project engi-neers to evaluate a total systemapproach. The cost of the rockboltitself, or such properties as tensilestrength, are seldom of primary inter-est. The decisive factors are the result-ing safety, the total cost, and the timerequired to fulfil the mission.

A productivity study comparingSwellex to other bolts in a gold mine

in Canada has proved that Swellexboosted metres of advance by 10%and reduced bolting costs by 10%. Asmore bolts were installed per workingshift, fixed costs for manpower andrigs were diluted, resulting inincreased metres of advance/shift withimproved safety. For similar reasons,Swellex has became a standard inmost European countries and in Japan.

To summarize, when the Swellexbolt is installed in heavily fissuredrock, the radial stresses enhance thecontact forces between blocks of rocksurrounding the bolt, leading to anincrease in rock mass strength. Insoils, Swellex bolts provide consolida-tion immediately around the bolt,leading to an increase in the strengthof the material, and improved anchor-ing capacity of the rockbolt. In hardrock, 0.5 m of anchored Swellex rock-bolt gives a pullout resistance equal tothe breaking load of the bolt. A stronganchorage capacity will help to dis-tribute the stress around the excava-tion and avoid stress concentrationclose to the surface that can lead torock falls or strain burst.

There are Swellex rockbolts foralmost any environment and purpose.Swellex Mn12 and Pm12 are perfectfor regular daily support in mining andtunnelling. When high loading capaci-ty is needed, Swellex Mn24 or Pm24is the answer. Swellex Mn16 andPm16 are a cost-effective solutionwhen 43-52 mm drilling is preferred.

In highly corrosive conditions, orwhere there are demands for long life,Coated or Plasticoated Swellex maybe the choice. In situations where verylong bolts are required, or in confinedspace, Mn24E Extendable Swellexoffers fast installation of up to 12 m-long bolts.

Recent years have seen the devel-opment of the Mn24H, a type ofSwellex that is part of the rock supportand is also used to hang heavy loadswithout inducing unfavourable stressin the bolt’s head bushing.

Atlas Copco is also proud of itslatest patented hybrid system of rockreinforcement, see article in this issue.

by Mario Bureau

TALKING TECHNICALLY


Hybrid bolt for long anchorage in rock.

RR3/RT3 11/8/05 15:33 Page 9

Document2 3/10/05 12:10 Page 1

New Tool

Atlas Copco research and develop-ment has engineered a new generationof Swellex bolt, which will better suitthe rock mechanical requirements. Atthe same time, it was decided to fur-ther increase the productivity, perfor-mance and reliability of Swellexpumps. By these means, a quantumleap forward in safety and perfor-mance has been achieved.

Loading capacity normally definesa class of rock bolt. For example,Standard Swellex is a 100 kN bolt,while Super Swellex is in the 190 kNcategory. But other parameters caninfluence the final performance of arockbolt, and especially its contribu-tion to safety.

Experience in mining and tun-nelling operations has shown thatelongation is a very important parame-ter in judging the performance of abolt. In deep mines, strain concentra-tion areas, uneven load, progressive

deformation and squeezing ground areall cases in which a bolt with a superi-or capacity to follow the rock de-formation can play an important rolein balancing and re-adjusting the strainfield towards stability. But elongationwithout tensile strength is simply outof the question.

Atlas Copco needed a new tool tomeasure the total performance of rock-bolts, and a new parameter capable ofcombining capacity and elongation.As the deformation is expressed inpercent (%) in the classical load defor-mation graph Atlas Copco is introduc-ing the Work Index (Wi). The WorkIndex (Wi) as real work is defined bythe integral of load in function of thedeformation also represented by thearea beneath the curve in Figure 1.The Work Index (Wi) gives a truthfulpicture of the total energy absorbed bythe bolt before breaking down, orlosing its function.

Search For ExcellenceThe Swellex range is based on severalhole sizes. Standard Swellex is used incombination with holes from 32 mmto 39 mm-diameter, while both Superand Midi Swellex work in the 43 mmto 52 mm range.

A possible solution to increase theWork Index was to increase the geo-metrical feature of the bolts.

Considering the Swellex position asan established worldwide commercialsuccess, it did not make sense tomodify its well-accepted and fit-to-application dimensions. It was morelogical to work on material propertiesand production methods.

The steel used in Swellex is alreadya special type, with few impurities.Well-established co-operation with aleading steel supplier and with a pipemill allowed a tailored technical speci-fication to be developed for materials,

TALKING TECHNICALLY


Figure 1. The excellent performance of the Super Swellex rockbolt is further improved by Swellex Mn24,the corresponding bolt in the new Manganese Line.

Swellex Manganese OffersImproved Work IndexTough NewcomerAtlas Copco’s Swellex rockbolts

have a long and successful his-

tory based on two simple advan-

tages for the customer: safety

and productivity. Swellex rock-

bolts are watertight, double-

folded, high-quality steel tubes,

which are expanded by a high-

pressure water pump through a

pre-drilled hole. The expansion of

the tube generates both contact

friction and mechanical interlock

between the steel and surround-

ing rock, giving immediate and

full-column rock reinforcement in

a simple and rapid way.

The latest range of frictional

bolts, marketed as Swellex Mang-

anese, will dramatically increase

performance, thanks to a new

steel composition and an innova-

tive heat treatment.

Wi Wi

RR3/RT4.qxd 23/6/05 9:05 Page 11

and a series of alloys and high tensilesteels were considered. Only a limitednumber of options can handle thesevere requirement of Swellex rock-bolts with respect to radial deforma-tion during expansion, and weldabilityto assure perfect watertight contacts atthe bushings. It was decided to use abetter quality steel, with a higher man-ganese content.

Produced in a cold forming mill,the steel reaches a very high tensilestrength and high loading capacity,but unsatisfactory elongation. A post-production heat treatment is then used toproduce the extraordinary elongationproperties needed for the Swellex profile.

Improved Behaviour

Figure 1 compares typical load/deformation curves for Super Swellexand the new Swellex Mn24. Inparticular, the regular Swellex steelprofile shows a classical behaviour forcarbon steel. Beyond the yieldingpoint (200 kN), the profile accepts alarge amount of deformation, but withslightly lower strength. When a 20%elongation is reached, the profilebreaks down.

The new, high-strength and fullyannealed Manganese Line now offers

a higher loading capacity and, at thesame time, enhanced elongation. Figure1 shows that, beyond yielding point,the manganese steel increases the loadcapacity due to the hardening process.

The curve continues to point up-wards until a 10% elongation isachieved, then a long horizontal seg-ment goes above the 30% level beforethe profile breaks up. This extraordi-nary behaviour gives the capacity toabsorb a substantially higher quantityof energy, as indicated in the 80%increase in the Work Index shown inFigure 2.

Total Reliability

The heat treatment used during theproduction of the new SwellexManganese Line further improvesrepeatability of the performanceobtainable by the bolts. A largenumber of pull tests, representative formillions of rockbolts, show very littlevariation in the results.

As a result, engineers, miners, rock-mechanics and consultants can rely onsafe and quality controlled rockbolts,through the entire process from manu-facturing to installation.

by Federico Scolari

TALKING TECHNICALLY


Figure 2. After a series of experiments, a heat-treated Manganese steel was chosen. This tableshows the results of the design efforts withrespect to tensile tests of the profile afterexpansion to simulate real conditions.

Summary ofSwellex® user

benefits

● Swellex provides cost-effective rockreinforcement in mostrock types and conditions.

● Swellex installationprocedure ensures thatevery bolt installed willprovide optimumreinforcement.

● Swellex rock bolts arequickly installed, and verylittle training is required touse the equipment.

● Swellex rock bolts providefull column interlock withthe surrounding rock,without the need formechanical lockingdevices or groutingagents.

● Swellex requires noenvironmentally harmfulchemical grouts to anchorthe bolt in the rock.

● The quick and easyinstallation, and theassurance that every boltprovides immediate fullload-bearing capacity,makes Swellex the mostcost-effective rockreinforcement.

Work Index forvarious types ofbolts.

RR3/RT4.qxd 23/6/05 9:05 Page 12

Competence Centre

The Rock Reinforcement CompetenceCentre team at Atlas Copco under-stands the requirements of differentrock reinforcement situations, and has

striven over the years to develop sup-port systems using the best availablesteel for each application.

Once the anchorage mechanismis understood, the best way to pre-dict how the rock support willinteract with the rock mass is tolook at the steel load-deformationgraph.

It is preferable to assess graphsfrom manufactured product instead ofthe virgin steel, as the manufacturingprocess will modify the property ofthe steel and the way the support willbehave under load.

Mn Line

Mn Line bolts are made out of highstrength steel, profiled, welded andheat-treated to survive extensivedeformation at maximum strength forhigh-energy consumption beforereaching failure. Furthermore, theplastic zone is characterized by a con-tinuous progression of the load thatallows, when the bolt is installed inrock, a progressive debonding. As thediameter of the loaded section reduces

TALKING TECHNICALLY


Manganese and Premium LinesContinuousImprovementAtlas Copco has, over the years,improved considerably theSwellex system. Rock engineersare extremely conscious that thebehaviour and efficiency of rockbolts can be dictated by the prop-erties of the steel from whichthey are made.

Accordingly, rock bolts are nolonger judged simply by theirmaximum tensile strength. Therock mass stresses surroundingunderground excavations haveto be tamed using energy ratherthan strength. Sometimes, it isbetter to bend with the stress,while in other instances stiffnessis preferable. It all depends onthe type of rock, excavation size,geology, stress field evolution,seismicity, corrosion andlongevity required.

Atlas Copco, which introducedthe Manganese Mn Line ofSwellex rock bolts a couple ofyears ago, has recently launchedthe Premium Pm Line.

Comparison tables for Mn and Pm bolts.

Mn12 Pm12Yield Load kN (Rp02) 75 100Min. Breaking Load kN 100 120Min. Elongation % 20 15Working index 2000 1800



S T R A I N ( % )

300

250

200

150

100

50

00 5 10 15 20 25 30 35

LO

AD

(k

N)

Pm24 Mn24

Typical load/strain graphs for Pm24 and Mn24 bolts.

RR3/RT5 23/6/05 9:06 Page 13

under plastic deformation, a succes-sion of new sections are progressivelyreleased to work and stretch, provid-ing extra energy absorbency andavoiding rapid failure.

Mn Line bolts are therefore bestsuited to an environment where rockmass stress is high and unstable,requiring good energy absorbencycapacity.

Typical applications for the MnLine are where deformation/stress ofthe rock mass is unstable in time.These situations occur in miningstopes, deep mining, mining in a highstress environment caused by poorgeology or faulting, and mining inzones where movement is expected inthe walls or roof resulting in stressincrease with time.

Premium Line

The Pm Line is also made of highstrength steel but having differentproperties than the steel used forthe Mn Line. No heat treatment isgiven to the Pm bolts, resulting in avery stiff behaviour at high load,because the yielding strength isvery close to the maximum tensilestrength.

Pm Line bolts are used where maxi-mum control of the rock mass conver-gence is targeted, and a high yieldingload capacity (Rp02) and stiffness arerequired, as in civil tunnelling projects.

Typical applications for the PmLine are where deformation/stress ofthe rock mass is stable in time andhigh stiffness is required. These situa-tions occur in tunneling, beam consol-idation of strata in mining, miningwhere the rock mass stress and move-ment are low or stable in time, and theyielding load will never be reached,and mining and tunnelling in soft rock.

Atlas Copco is continuously invest-ing in research and development tooffer the market the best rock rein-forcement products with safety andproductivity in mind. The right steelfor the application adds safety andproductivity!

by Mario Bureau

TALKING TECHNICALLY


Choice of Reinforcement Type

Conditions Properties of Preferred Reinforcement/reinforcement Support Types

Soft Rock and low to High Stiffness Swellex Pm Linemedium stresses

Soft Rock and high Stresses Yielding and high Swellex Mn Line + Weathered hard rock or laminated/ anchorage Connectable and Hybridschistose rock and high stresses

Hard Rock and low to High Stiffness Swellex Pm Line + medium stresses Swellex Hybrid cemented

Hard Rock and high Yielding and retention Swellex Mn Line +Stresses capacity Swellex Hybrid non-cemented

for rock burst (seismicity & strain bursting)

Checking nut and plate on Swellex Premium bolt.

RR3/RT5 23/6/05 9:06 Page 14

MAI SDA Functional Parts

The system elements of the AtlasCopco MAI Self Drilling Anchor(SDA) are as follows:

The Atlas Copco MAI bar, which ismanufactured from API standardheavy walling steel tubing, cold rolledto form a standard ISO rope threadprofile. The rolling process refines thegrain structure of the steel, increasingthe yield strength, and producing adurable drill rod suitable for a range ofapplications. The standard rope threadof the Atlas Copco MAI bar producesan excellent bond between the bar andgrout, as well as enabling connectionto all Atlas Copco Boomer and surfacedrill rigs, and use with a wide range ofdrill steel accessories.

The MAI bar is produced in 12 mlengths and then cut to size dependingon customer requirements. Standarddelivery lengths are 1 m, 2 m, 3 m, 4 m and 6 m. Recommended maximumbar lengths depend on diameter and canbe up to 6.0 m. Additional lengths upto 12.0 m are available on request.

The Atlas Copco MAI coupler, whichfeatures a patented design that enablesdirect end-to-end bearing between eachbar, reducing energy loss and ensuringmaximum percussive energy at the drillbit. The coupler design has a threadarrangement in which the top half of the thread is rotated against that of thelower half, providing a centre stop foreach bar. All couplers exceed the ulti-mate strength of the bar by 20%.

To enable the correct seating ofeach bar within the coupler, all barshave a precision cut at right angles toenable end to end bearing. A quarterturn back of the coupler on the lowerbar will ensure optimum seating of theupper bar within the coupler.

The Atlas Copco MAI hexagonalnut, which is machined with chamferededges on both ends from high precisionsteel, and tempered to meet any strin-gent demands of the anchor specifica-tions and the daily operations ofunderground works. All nuts exceedthe ultimate strength of the bar by 20%.

The Atlas Copco MAI bearingplate, which is a formed steel platewith a centre hole, allowing articula-tion of seven degrees in all directions.All functional parts are constantlytested, in line with the company’s rig-orous quality assurance policy.

The sacrificial Atlas Copco MAIdrill bit is the most crucial part of theanchor system, and is responsible forthe productivity of the installation.Atlas Copco MAI maintains a largerange of drill bits to suit the changingdemands of geology encountered ondifferent projects. In order to improveon performance and cost efficiency,

TALKING TECHNICALLY


Hollow-Core Self DrillingAnchoring SystemsSupport WithoutCasingThe Atlas Copco MAI Self DrillingAnchoring System is a fullythreaded steel bar which can bedrilled and grouted into loose orcollapsing soils without the useof a casing. The bar, or SDA,features a hollow bore for flush-ing, or simultaneous drilling andgrouting, and has a left-handrope thread for connection tostandard drill tooling.

The Atlas Copco MAI SDA canbe installed in a variety of differ-ent soils and ground conditionsranging from sand and gravel toinconsistent fill, boulders, rubbleand weathered rock, as well asthrough footings and base slabs.

Applications associated withunderground works include:radial anchoring for stabilizationof tunnel circumference duringNATM-style excavation; as fore-poles, spiles or umbrella foradvance protection of the exca-vation; as root piles for reactionload of steel support arches; andfor slope stabilization of thetunnel portal.

MAI SDA arrangement, showing threaded bar,coupler, nut, plate and bit.

RR3/RT6.qxd 23/6/05 9:32 Page 15

data is collected from projects aroundthe world, and incorporated into thedesign with the aim to improve pene-tration rate and bit quality, and toreduce manufacturing costs.

Overall Advantages of MAISDAAdvantages of the Atlas Copco MAISDA system are that it is particularlysuitable for very difficult and unstableground conditions, such as broken,fissured and fractured rock formations,or unconsolidated sands and gravels.Re-drilling time due to collapsingboreholes is avoided, and speed ofinstallation is high, with no primarydrilling required. The drilling, placingand grouting of the anchor is per-formed in one single operation,reducing the drill labour compared tocased boreholes.

Since conventional rotary-percus-sion drilling equipment is used, themethod of installation is very similarfor all ground conditions, and the boltscan be installed in all directions,including upwards.

There is an option to use simultane-ous drilling and grouting techniquesduring installation, to consolidate anysurrounding loose ground.

The anchor bar consists of a fulllength left hand rope thread, whichgives the flexibility to adjust the barlength to the actual requirement. Thisis especially useful if anchoring has tobe performed in a confined workspace.

Method of Installation

Self Drilling Anchors are installedwith air driven or hydraulic rotary per-cussion drilling equipment, using a

borehole flush medium suitable for thespecific ground conditions.

There are three types of boreholeflush: 1) water flush for long bore-holes in dense sand, gravel formationor rock conditions, for a better trans-portation of large cuttings and coolingof the drill bit; 2) air flush for shortboreholes in soft soil, such as chalkand clay, where water spillage is to beavoided; 3) simultaneous drilling andgrouting (SDG), for all lengths ofboreholes in all unconsolidated soilconditions.

Using SDG, the grout stabilizes theborehole during installation, providinga better grout cover along the nailshaft. The grout has good penetrationinto the surrounding soil, so higherexternal friction values are reached,and the installation is completed in asingle drilling operation, saving time.

By utilizing a sacrificial drill bit,the MAI SDA is drilled continuouslyforward without extraction, until thedesign depth is reached. To reach arequired nail length of 12-15 m, the 3to 4 m standard rod lengths are easilycoupled together.

When using the first two flushingmedia for the drilling operation, thesoil/steel interface has to be created bygrouting through the hollow stem ofthe anchor rockbolt. The grout exitsthrough the flush holes of the drill bit,and backfills the annulus around theanchor that has been cut by the largerdiameter of the drill bit.

For simultaneous operation, theflushing medium is already a grout mix,which has the ability to harden after theinstallation process is completed.

by Mark Bernthaler

TALKING TECHNICALLY


Installation sequence of MAI SDA.

MAI PUMPThe Oneand Only

RR3/RT6.qxd 23/6/05 9:33 Page 16

Atlas Copco MAI SDATechniquesPost installation groutingA number of Atlas Copco MAI SDAbolts are installed in one phase to limitthe working time of the drilling equip-ment and make it available for otherdrilling operations within the excava-tion cycle. The grouting is performedas an independent operation from aseparate support vehicle.

Installation and successive groutingIn order to utilize this system, anIntegrated Rotary Injection Adapter(Ceminject) is mounted between the

COP hammer and the anchor bar.Drilling is carried out using water orair flushing, but, upon reaching theplanned borehole depth, a suitablecement mix is immediately injected.By slow rotation while applyingbackwards and forwards movementof the SDA, the grout is pushed underpressure from the bottom of the bore-hole towards the borehole mouth. Itmixes in the borehole to provide opti-mum backfilling of the boreholeannulus contact to the soil. Theadvantage of this system is the reduc-tion of cement consumption in hori-zontal boreholes.

Simultaneous drilling and groutingSimilar to the successive groutingmethod, this system also requires theuse of a Integrated Rotary InjectionAdapter (Ceminject). However,instead of drilling with air or waterflush, a suitable grout mix is intro-duced. The following advantages areachieved: stabilization of the

borehole and optimum filling of theannulus; improved protection againstcorrosion; and consolidation of gravel,fissures, fractures or voids surround-ing the borehole.

Time Saving

Atlas Copco envisages full mecha-nization of the Atlas Copco MAISDA to reduce the installation timeand increase its productivity. Thecompany is also interested in resolv-ing particular site problems, and inadvancing tunnel technology for typi-cal applications of Self DrillingAnchors. These are, in particular:radial nailing of the tunnel circumfer-ence; forepoling for cylindrical tunneladvance, using lengths of approxi-mately 4 m with 1 m overlap and facestabilization using lengths up to 15 m,and root piles.

Worldwide, underground projectsare designed with geological expecta-tions based on information received

TALKING TECHNICALLY


Integrated Rotary Injection Adapter (Ceminject) mounted on a Boomer.

Atlas Copco MAI Self DrillingAnchorsProductivity andProblem SolvingThe Atlas Copco MAI SDA is aunique bolting solution for un-stable ground conditions such assand, gravel, silt, and clays, andin soft to medium fractured rockformations.

When discussing productivity,only projects facing such groundconditions should be considered.Conventional rockbolts, or soilnails, generally have the dis-advantage that, when beinginstalled in poor ground condi-tions, unproductive time is spenton measures such as: retrievingexpensive drill tools from col-lapsed boreholes; repositioningthe drill feed to clean collapsedboreholes; introducing the grouthose to the borehole bottom, andgrouting the borehole; andinserting the nail or rockbolt withthe assistance of the feed systemof the drilling unit.

The Atlas Copco MAI SDAsystem is designed to avoid mostsuch time losses. With an opti-mized installation method, tail-ored to the project’s needs, theultimate aim should be to limitthe installation time to the actualdrilling time of the borehole.

RR3/RT7 23/6/05 9:34 Page 17

from rather limited soil investigations.Furthermore, today’s need to satisfythe design requirements for infrastruc-ture projects mostly doesn’t allow aroute selection that follows only goodrock conditions. This increasinglydemands flexibility by the contractor,who may be forced to adjust at shortnotice to unpredicted changes in geo-logical conditions.

Construction sites today have theoption to cater for every eventuality,and to maintain tools at site for everytype of ground condition. Prior plan-ning by the site management to main-tain sufficient quantities of AtlasCopco MAI SDA available for use can

allow an immediate intervention,reducing time wastage and increasingproductivity.

The design of the Atlas Copco MAISDA also favours productivity interms of storage and handling.

Anchor bars with a continuous lefthand thread are delivered to site instandard lengths of 2 m, 3 m, 4 m and6 m, and can be assembled to the spe-cific lengths required. Transport tosite, and onward to the working area,is simplified, due to the short lengthsof the anchor elements and theiraccessories.

by Mark Bernthaler

TALKING TECHNICALLY


Time savings by using MAI SDA System.

Delivery lengths of Atlas Copco MAI SDA.

RR3/RT7 23/6/05 9:34 Page 18

More Applications

The ODEX method of overburdendrilling with an eccentric bit is wellestablished amongst drillers, particu-larly when it comes to shallow, smalldimension holes. Now, with the intro-duction of the Symmetrix system,Atlas Copco has opened the door to aninfinite number of applications wherecasing drilling is the preferred solutionfor forepoling, micropiling and othertypes of ground engineering work.Symmetrix enables drillers to golarger and deeper than ever before.

Whereas the ODEX method is idealfor drilling holes up to 273 mm indiameter, Symmetrix handles theinstallation of casings up to 1.2 m indiameter, in holes of 100 m-deep (300 ft)and beyond.

This unique capability gives con-tractors the power to tackle any typeof casing advancing work, frommicropiling, tunnel forepoling, andfoundation piling, to opening ‘rat-holes’ for oil and gas wells, as well ashorizontal casing drilling.

In addition, the Symmetrixsystem is a perfect complement toAtlas Copco’s extensive range ofDTH (Down-The-Hole) equipment.The Secoroc DTH hammers for

overburden drilling, the specially-designed Mustang rigs for anchordrilling and micropiling, and theDTH products provided by AtlasCopco Drilling Solutions in theUS, provide sufficient combina-tions to meet most overburdenchallenges.

Case for Casings

There is no doubt that the use ofdrilled casings in underground con-struction is becoming increasinglypopular worldwide, primarily due tothe expansion of building and infra-structure growth in areas that are lessthan ideal for such development.

Pile driving in dense urban condi-tions can disturb surrounding structuresor utilities, and is often difficult toestimate in terms of costs. This iscompounded by other problems, suchas ground settlement, soil compactionand lateral soil displacement.

When using a drill casing, soil, rockand other debris are removed within aprotective steel tube and brought tothe surface. For foundations, during

the concreting process the support istransferred from the temporary drillcasing, which is gradually withdrawn,to the concrete that forms the pileshaft. Likewise, the casing may be leftin place as additional structural sup-port, or for protection of the pile. Forexploration and well drilling, thecasing can become the conduit forbringing the debris to the surface.

For these reasons, designers andowners turn to drilled casings, and DTHdrilling with Symmetrix is often the onlymethod that can drill through all groundconditions, boulders and solid rock.

Symmetrix in SensitiveConditionsThe Marina Palace Hotel, a large hoteland congress center located in the oldcity of Turku on the south westerncoast of Finland, is going through amain renovation scheme.

Part of the project is to enlarge theparking capacity by building an under-ground parking lot. Ground conditions

TALKING TECHNICALLY


Larger and Deeper Holes WithSymmetrix New World ofConstructionWhen Atlas Copco acquired theRotex company of Finland in2004, it represented a major stepforward for contractors in thefield of overburden drilling andrelated technologies. In additionto its well-proven ODEX equip-ment, Atlas Copco is now able tooffer Symmetrix, a uniquesystem that enables drillers todrill deeper and larger holes thanever before.

Symmetrix RC system used in Turku, Finland.

RR3/RT8 23/6/05 9:53 Page 19

in Turku are problematic, withmainly post glacier clays at surfaceoverlaying sand layers containinghigh water pressure. This is followedby till containing very hard boulderstypically sitting on steeply inclinednon-weathered hard granite or dia-base.

The old town is built mainly onwooden driven piles. These are beingreplaced by steel casings drilled all theway to bedrock, for which severalunderpinning projects are underway onthe northern banks of the Aura river.

In the Marina Palace Hotel parkinggarage project, clay and till layersreach 35 m-deep in the northerncorner of the site, and the till is 65 m-

deep on the southern riverside. For thegarage foundation, steel casings arebeing drilled 1 m or 2 m into the solidbed rock, which means that longestcasings are 67-68 m-long. Drillingwork is being carried out by Skanskaand their subcontractor, SotkamonPorakaivo. Casing sizes are from 140mm to 508 mm, all of which are thickwalled to form load bearing members.

Most of these casings are in sensi-tive conditions very close to existingbuildings and their foundations, so aunique drilling system is required.

Atlas Copco Rotex has developedreverse flushing drill bits in order tocontrol the air flushing in sensitiveconditions. Symmetrix RC is designedto give the straightness the consultingengineers require, control of flushingmedia needed under existing founda-tions, and high productivity in virtual-ly any ground condition.

The Symmetrix RC system specifiedby the supervising design engineeringcompany for the Marina Palace Hoteljob is being used on all four drillrigs.

Hard, rubber-like clays are normallyexpected to be problematic, but sub-contractor Sotkamon Porakaivo reports

TALKING TECHNICALLY


Completing a deep pile at Marina Palace Hotel,Turku.

Principle of the Symmetrix system

1) The casing tube is drilled to therequired depth.

2) The pilot bit is withdrawn from thecasing.

3) The casing is left in the hole as asupport for the pile.

ROTARY MOTOR

COMPRESSOR

CUTTINGS

CASING PIPEOVERBURDEN

DUAL WALLDRILL PIPE

INTERCHANGE

CASING SHOE

SYMMETRIX BIT

1 2 3

RR3/RT8 23/6/05 9:53 Page 20

that Symmetrix RC has made drillingvery easy and productive, with casingsgoing in very straight and fast all theway through clays, sands, boulders,till, and even into very hard bedrock.

Symmetrix Secret

So what makes the Symmetrix casingadvancing method so unique? Basically,the secret lies in the patented design of

the locking mechanism and flushingholes. The system consists of threemain components working together asa single unit – a pilot bit with largeinternal flushing holes and externalflushing grooves, a symmetrical ringbit (reamer) with internal bayonet cou-pling, and a casing shoe for driving thecasing.

The pilot bit is attached to the ringbit with a bayonet coupling. Togetherthey rotate clockwise and cut a hole suf-ficiently large to allow the casing shoeto pull down the casing pipe. The ringbit rotates freely on the casing shoe,which is welded to the casing. Duringdrilling, the casing does not rotate.

Casings can be added to the string asrequired. The flushing air is ejectedthrough the holes in the face of the pilotbit, and returns immediately up widegrooves between the pilot bit and ringbit and the annulus between the casingand the drill string. This ensures highflushing velocity with low hole degrada-tion.

When the hole is complete, thepilot bit is unlocked from the ring bitwith a slight counter-clockwisemotion, and withdrawn up through thecasing. The casing can then be eitherleft in place or retrieved from the hole.

Future Development

The technology of casing drilling isconstantly developing, and thedemand is increasing fast in many dif-ferent applications.

One of the biggest growth areas isin drilling in urban environments,where it is no longer possible to openup the streets for further drilling workwithout disturbing vital installations.Here, Symmetrix will have a majorrole to play.

Large city subways are typicalcases where tunnel roofs have to bepipe-drilled in order to connect oneunderpass to another. With Symmetrixon board, Atlas Copco is able to pro-vide customers with state-of-the-artcasing drilling technology that canmeet these challenges, and many morebesides.

by Jukka Ahonen Product Manager, Atlas Copco Rotex

TALKING TECHNICALLY


What it means for the contractor Symmetrix systems come in a large number of versions and sizes to suit a widerange of applications. These include: piling; forepiling and micropiling usingboth temporary and permanent casing; underpinning with grouted columns; welldrilling; and horizontal casing drilling. For the overburden drilling contractorthis means: straight holes without risk of deviation; quick setup and high pro-duction rates; less torque required in all formations; easy to lock and relock;convenient drilling at any angle; no jamming and lost bits; can be used in allground conditions and at any angle down to 100 m (300 ft) and beyond; andsignificant economic savings.

Drilling close to existing structures.

RR3/RT8 23/6/05 9:53 Page 21

TALKING TECHNICALLY


Sacrificial Drillbits

RR3/RT9.qxd 23/6/05 9:57 Page 22

TALKING TECHNICALLY


RR3/RT9.qxd 23/6/05 9:57 Page 23

TALKING TECHNICALLY


Specializing for Safety

There was a time when undergroundmining and safety were terms not com-monly referred to in the same sentence.However, times have changed, andtoday safety is given a place of promi-nence in the operational priorities ofthe mining industry.

Freshly blasted openings leave con-siderable areas of loose rock, whichmust be removed to prevent fall-of-ground injuries. Improvements indrilling and blasting techniques havehelped to significantly reduce theamount of this loose rock. Scaling,which is the most hazardous part of thework cycle, is used to remove the visi-ble loose rock.

Subsequent blasting might result inadditional rock falls, especially in frac-tured ground conditions. Screening orshotcreting, as a means of retention ofthis loose rock, is often used in combi-nation with rockbolting. Screening,which is a time-consuming operation,

is common practice in Canada andAustralia.

Since the 1960s and 1970s, consid-erable effort has been spent on mecha-nizing underground operationalactivities, including the rock excava-tion cycle. Within the drill-blast-muckcycle repeated for each round, thedrilling phase has become fully mecha-nized, with the advent of high produc-tivity hydraulic drill jumbos.

Similarly, blasting has become anefficient process, thanks to the devel-opment of bulk charging trucks andeasily configured detonation systems.After only a short delay to provide foradequate removal of dust and smokeby high capacity ventilation systems,the modern LHD rapidly cleans out themuck pile.

These phases of the work cyclehave been successfully mechanized,and modern equipment provides a safeoperator environment.

By contrast, the most hazardous oper-ations, such as scaling, bolting andscreening, have only enjoyed limitedprogress in terms of productivityimprovements and degree of mechaniza-tion. The development of mechanizedscaling and bolting rigs has beenslower, mainly due to variations in

safety rules and works procedure inspecific rock conditions.

To summarize, equipment manufac-turers have had difficulty in providingglobally accepted solutions.Nevertheless, there is equipment avail-able to meet most of the currentdemands from miners and tunnellers.

However, there is a perception thatequipment for full mechanization ofrockbolting is expensive, and a large-scale consumer of parts and compo-nents.

Mechanization Stages

Various methods of mechanized boltingare available, and these can be listedunder the following three headings.

manual drilling and boltingThis method employs light hand heldrock drills, scaling bars and bolt instal-lation equipment, and was in wide-spread use until the advent of hydraulicdrilling in the 1970s. Manual methodsare still used in small drifts and tunnels,where drilling is performed with hand-held pneumatic rock drills. The bolt holesare drilled with the same equipment, orwith stopers. Bolts, with or without grout-ing, are installed manually with impact

Mechanized Bolting andScreeningUtilization is theKeyFor civil engineering applicationssuch as tunnelling, it is quitecommon to use the same equip-ment for all drilling requirements.These days, a single drillrig canaccommodate drilling for faceblasting, bolt holes, protectionumbrellas, and drainage. As thereare normally only one or twofaces available for work beforeblasting and mucking, it is diffi-cult to obtain high utilization forspecialized equipment such asmechanized bolting rigs.By contrast, in undergroundmining, especially where anumber of working areas areaccessibleusing methods such as room andpillar, high utilization of special-ized equipment can be expected.

Mechanized bolting underway using Boltec.

RR3/RT10 23/6/05 10:00 Page 24

wrenches. To facilitate access to highroofs, service trucks or cars, with elevat-ed platforms, are commonly used.

semi-mechanized drilling andboltingThe drilling is mechanized, using ahydraulic drill jumbo, followed bymanual installation of the bolts byoperators working from a platformmounted on the drill rig, or on a sepa-rate vehicle. The man-basket, as aworking platform, limits both the prac-tical working space and the retreatcapability in the event of falling rock.In larger tunnels, the bolt holes aredrilled with the face drilling jumbo.

fully mechanized work cycleA special truck, equipped with boommounted hydraulic breakers, performsthe hazardous scaling job, with the

operator remotely located, away fromrock falls. Blast holes are drilled in theface using a drill jumbo, and all func-tions in the rock support process are per-formed at a safe distance from the rockto be supported. The operator controlseverything from a platform or cabin,usually equipped with a protective roof.

Where installation of steel mesh isundertaken, some manual jobs maystill be required. Mesh is tricky tohandle, because of its shape andweight, and this has hampered devel-opment of fully automated erection.

Quality of Bolting

In 1992, it was reported that indepen-dent studies were indicating that asmany as 20-40 % of cement and resingrouted bolts in current use were

non-functional. Tunnellers werereporting that they were not installingbolts close to the working face,because they might fall out when blast-ing the round. Obviously, a large pro-portion of rockbolts were beinginstalled for psychological reasons,rather than for good face support and asafe working environment.

However, by using a mechanizedinstallation procedure, the quality ofinstallation improves. The bolt can beinstalled directly after the hole hasbeen drilled; the grout can be measuredand adjusted to the hole size; and boltinstallation can be automated, which isespecially important when using resincartridges, where time and mixingspeed are crucial.

It can be proved that mechanizationand automation of the rockboltingprocess offers improved quality andsafety.

While mining companies and equip-ment manufacturers, especially inCanada, focused their development onimproving semi-mechanized roof sup-port, evolution in Europe concentratedon fully automated bolting.

During the 1990s, progress acceler-ated, and today, around 15 % of allbolting in underground mines world-wide is carried out by fully mecha-nized bolting rigs.

However, compared to mechaniza-tion of face drilling and productiondrilling, this level of acceptance is farfrom impressive, and the industry hasbeen slow to accept the principle. Themore obvious positive safety aspects ofmechanized rockbolting have beensidelined by considerations relating tothe scale of operations and the type ofequipment available. Hence the higheracceptance in mining, where severalfaces are operated simultaneously. Fortunnelling applications, where the rateof advance is of prime importance, theeconomic criteria might be different.

Also, as there are more functionsincorporated into the average rock-bolter when compared to a drill jumbo,maintenance takes longer, and moreparts and components have to bereplaced. Bolting units are exposed tofalling rock, or cement from grouting,both of which impact upon mainte-nance costs.

TALKING TECHNICALLY


New generation Boltec LC rig installing screen.

RR3/RT10 23/6/05 10:00 Page 25

Significant Improvements

When Atlas Copco introduced its newseries of mechanized rock bolting unitsin late 2001, a wide range of radicalimprovements was incorporated.

Based on the unique single feedsystem with cradle indexing, the newmechanized bolting unit, MBU, is con-siderably more robust, and less sensi-tive to falling rock, than itspredecessor. Holes are easy to relocate,and the stinger cylinder improves col-laring and the ability to install boltsunder uneven, rugged roof conditions.Major re-engineering has resulted in30% fewer parts. Less maintenanceand stock inventory are required, andhigh availability has been recorded.

Furthermore, the chain feeds used inthe new Boltec series feature an auto-matic tensioning device, which guaran-tees even and strong feed force for therock drill, while a stinger cylinderimproves collaring and the ability towork under uneven roof conditions.

The completely redesigned drillsteel support provides sufficient spacefor bolt plates passing through, andfacilitates extension drilling.

The most outstanding benefit, how-ever, is the computer-based rig controlsystem, RCS. This system, which hasalready been successfully incorporatedon the latest Boomer and Simba seriesof drillrigs, offers simplified fault detec-tion, operator interactivity, and the basisfor logging, storing and transferring ofbolt installation production and qualitydata.

The Boltec is equipped with thenew rock drill, the COP 1532, which isshort and compact, and features amodern double dampening systemwhich, combined with the RCS, trans-mits maximum power through the drillstring. The long and slender shapedpiston, which is matched to the drillsteel, permits high impact energy andlong service life of all drilling consum-ables.

Versatility and Ergonomics

Modern bolting rigs can handle instal-lation of most types of rockbolts, suchas Swellex, as well as resin andcement grouted rebars. Using the new

Boltec series based on RCS, the opera-tor copes easily with the moredemanding cement grouting and resincartridge shooting applications, bycontrolling all functions from thecabin seat. Up to 80 cartridges can beinjected before the magazine needsrefilling. Also, because meshing isoften carried out in combination withbolting, an optional screen arm can befitted parallel to the bolt installationarm, to pick up and install the bulkymesh screens. Up to 10 different pre-programmed cement-water ratios, andvarious additives, can be remotelycontrolled.

The new generation rigs offer theoperator a modern working environ-ment in a safe position. Low posi-tioned, powerful lights provideoutstanding visibility of the entiredrilling and bolting cycle.

The new Boltec family has twomembers: the Boltec MC, for boltlengths of 1.5-3.5 m and roof heightsup to 8 m; and the larger Boltec LC forbolt lengths of 1.5-6.0 m, primarily forlarge tunnelling projects having roofheights of up to 11 m.

The initial positive response fromoperators and mechanics confirms thatthe new generation of Boltec will pavethe way for further acceptance ofmechanized bolting.

Screen Installation

In Canadian mines the combination ofrockbolts and screen, or wire mesh, iscommonly used for rock support. Sincerock reinforcement is potentially one ofthe most dangerous operations in thework cycle, mechanized rockboltinghas become more popular. A computer-ized Boltec MC, equipped with screenhandling arm, has been in use for acouple of years at Creighton Mine,installing screen with split-set bolts.

In general, the screen is 3.3 m-longx 1.5 m-wide, and is installed in bothroof and walls, down to floor level.Typical spacing of bolts is 2.5 ft. Threedifferent types of bolts are used,depending on rock conditions, and allbolting must be done through thescreen, with the exception of pre-bolt-ing at the face. In general, galvanizedsplit-set are used for wall bolting,while resin grouted rebar or mechani-cal bolts are used in the roof, andSwellex in sandfill.

Once the screen handling arm haspicked up a screen section and fixed itin the correct position, the powerfulCOP 1432 hydraulic rock drill quicklycompletes the 35 mm diameter, 6 ft and8 ft holes. The bolting unit remainsfirmly fixed in position after the hole isdrilled, and the cradles are indexed,

TALKING TECHNICALLY


Boltec MC equipped with screen handling arm.

RR3/RT10 23/6/05 10:00 Page 26

moving the bolt, with plate, into posi-tion. The bolt feed, combined with theimpact power from a COP 1025hammer, is used for installing split-setbolts. The complete rock reinforcementjob is finished in just a few minutes.

Boltec MC Flexibility

The Boltec MC delivered to theCreighton mine is capable of handlingseveral types of bolts: split-set, mechan-ical-anchors, resin grouted rebar andSwellex. The switch of accessoriesbetween different bolt types takes 5-10minutes. To minimize water demandduring drilling, water-mist flushing isused. The Boltec MC can also beequipped with a portable operator’spanel connected by a 50 m-long cable.

Cartridge shooting is remote con-trolled for the Boltec MC, and up to 80cartridges can be injected before refill-ing is needed. A unique feature is thepossibility to use two different types ofcartridges, with fast or slower curingtimes, housed separately in the dualcartridge magazine. The operator canselect how many cartridges of eachtype to inject into any hole. Forinstance, he can inject two fast curingcartridges for the bottom of the hole,and follow up with slower-curing car-tridges for the rest of the hole, all with-out leaving his operator’s panel!

Cabletec L for CableBoltingAtlas Copco has developed a fullymechanized rig for drilling and cablebolting by a single operator. The firstunit is in operation at Outokumpu’sKemi chromite mine in northernFinland, and a second unit has gone toChile. The Cabletec L is based on thelong hole production drilling rig SimbaM7, with a second boom for groutingand cable insertion.

The booms have an exceptionallylong reach and can drill a line of up to4.7 m of parallel holes from the same rigsetup. Likewise, the booms can reach upto 7.8 m roof height, allowing theCabletec L to install up to 20 m-longcable bolt holes in underground miningapplications such as cut and fill miningand sub level stoping. Furthermore, the

drill unit can rotate 360 degrees and tilt10 and 90 degrees, backwards and for-wards respectively. The new rig isdesigned on proven components andtechnology featuring two booms - onefor drilling and the other for groutingand cable insertion. It also features anon-board automatic cement system withWCR (Water Cement Ratio) control. Allthese features facilitate a true singleoperator control of the entire drilling andbolting process. The two boom concepthas drastically reduced the entire drillingand bolting cycle time and, by separat-ing the drilling and bolting functions, therisk of cement entering the rock drill iseliminated. The operator is able to payfull attention to grouting and cable inser-tion, while drilling of the next hole aftercollaring is performed automatically,including pulling the rods out of thehole.

Cabletec is equipped with the wellproven COP 1838 ME hydraulic rockdrill using reduced impact pressurewith R32 drill string system for 51 mmhole diameter or R35 for 54 mm holes.Alternatively, the COP 1638 rock drillcan be used. Maximum hole length is

32 m. The cable cassette has a capacityof 1,700 kg and is readily refilledthanks to the fold-out cassette arm. Thecement mixing system is automated,comprising a cement silo containing1,200 kg of dry cement. The cement ismixed according to a pre-programmedformula, resulting in a unique qualityassurance of the grouting process. Thecement silo capacity is adaptable for upto 20 m-long, 51 mm-diameter holes.

To date, most holes have beendrilled in the 6-11 m range, for whichthe rig has grouted and installed cableat a rate of more than 40 m/h.Depending on type of geology and holediameter chosen, the drilling capacitycan vary between 30 and 60 m/h.

Conclusion

Rock support, including scaling, bolt-ing, screening, and cablebolting, is stillthe bottleneck in the working cycle inunderground mining and tunnelingapplications. Clearly, any reduction inthe time required to install the neces-sary support has a direct impact on theoverall cycle time, and consequentlythe overall productivity and efficiencyof the operations. The fully mecha-nized bolting rig of today, incorporat-ing all of the benefits of moderncomputer technology, constitutes amajor leap towards improved produc-tivity, safety and operator environment.

by Hans Fernberg

TALKING TECHNICALLY


Stoping sequence at Kemi underground mine. Cabletec drilling upwards, and Simba drilling downwards.

Cabletec main technical

data

Length: 13.9 m

Width: 2.7 m

Height: 3.3 m

Turning radius: 4.3m / 7.5 m

Cabletec

Simba

RR3/RT10 23/6/05 10:00 Page 27

TALKING TECHNICALLY


Swellex Rockbolts

Regardless of manufacturing origin,installation of rockbolts of lengths of 4m and upwards is normally a heavyand troublesome operation. TheSwellex Pm24 or Mn24 rockbolt is noexception. However, by adding a fewoptional items, a standard Atlas CopcoRocket Boomer can be modified totake care of most of this work. It willinsert the Swellex Pm24 or Mn24 intothe hole, fully inflate it to optimalcapacity, and even test it! Not only isit quick and easy, but also safer thanthe traditional manual method. Top ofthe list of optional components is aservice platform to assist with the highlevel holes. An onboard Swellexhydraulic pump is advisable, and, formanual insertion, a Swellex handle

with Swellex chuck, or, for mecha-nized insertion, the new Swellexchuck mounted on the COP hammer.For mechanized handling of the drillsteel, a Rod Adding System (RAS)can be mounted on the feed. For semi-mechanized installation, the followingcycle of operations can be used: selecta drill steel length that is slightlylonger than the length of the bolt to beinstalled; drill the bolt hole at thechosen spot, and to the full length;

keep the feed at the drill hole, andrecover the drill steel by the RAS grip-pers; attach the Swellex chuck to theCOP hammer; manually locate theSwellex bolt with faceplate in the drillsteel support at the top; insert theSwellex bolt into its final position in

Using Rocket Boomers to InstallRockboltsAdaptability forDrilling andInstallationWhen a contractor undertakes anunderground drill/blast excava-tion project, it is of utmostimportance to have the mostsuitable equipment available,both for blast hole drilling, andfor rockbolt drilling and installa-tion. For most situations, theAtlas Copco Rocket Boomer isthe best possible unit to choose.

This is true, not only for itsdrilling capacity, but also for itsadaptability to semi-mechanizedinstallation of some of the mostfrequently used rock bolt sys-tems, such as Swellex rock boltsand MAI Self Drilling Anchors(SDA). This affords the contractorthe option of using a single drill-rig to cover all face drilling androckbolt installation operations.On some contracts, this canmake the difference betweenprofit and loss. On bids, it canprovide the margin for the con-tractor that swings the award.

Atlas Copco Rocket Boomer, with its very capable BUT booms, is suitable for all kinds of rockreinforcement.

The new Atlas Copco Swellex Pm24Cand Mn24C features improved workabsorption capacity by way of elongationand load taking.

RR3/RT11 19/7/05 8:45 Page 28

the drill hole, using the feed-forcefrom the hammer; and inflate theSwellex bolt using the on-boardhydraulic Swellex pump. All done,and ready for the next bolt!

Connectable Swellex

When there is a need for very longbolts to be installed in a narrow drift,tunnel or cavern, the solution can bethe Swellex Pm or Mn 24C con-nectable rock bolt. This system com-prises three different types of boltsection that can be combined to practi-cally any required length. Each ofthese three sections is characterized byits function. The first section is sealedat its top end and threaded at its bottomend. The middle sections are threadedat both ends, and the bottom section isthreaded at one end and designed to fitinto the Swellex chuck at the other.The sections are threaded together toform a tight connection. InstallingSwellex Pm or Mn 24C utilizes thesame optional components as for theinstallation of long Swellex bolts, withthe addition of either the BSH 110Swellex version, or by using a Swellexretainer to keep the connectableSwellex in place when tying inSwellex sections. The RAS system cangreatly assist handling of the SwellexPm 24C or Mn 24C sections, using itstwo gripper arms attached to the BMHfeed, which are remotely controlled bythe Boomer operator. The bolt hole isdrilled to full depth using extension

drill rods. Recommended drill holediameter is 45-48 mm, with maximum51 mm, using R28 drifter rods with acoupling diameter of 44 mm. Theinstallation sequence is as follows:drill the bolt hole a little bit longer thanthe full bolt length; recover the drillstring, and remove it from the feed;place the top-section of the SwellexPm 24C or Mn 24C into the drill steelsupport, and feed the bolt section intothe drill hole, either manually, or usingthe COP rock drill; grip the bolt withthe BSH 110, or the retainer; thread inthe required number of middle sections

using the feed and the COP rock drill;grip the bottom of the string with theBSH 110, and attach the bottom endsection of the connectable Swellex,with faceplate; feed it into place usingthe rock drill and Swellex chuck; con-nect the Swellex pump, and inflate thebolt. It will take a few seconds to fullyexpand the complete bolt. When thepump stops, the bolt is ready to take itsfull 24 t load.

Swellex Hybrid

The Swellex® Hybrid consists of aSwellex bolt coupled with one or moreMAI Self Drilling Anchors (MAISDA®). A special connection cou-pling welded on to the Swellex bolt,enables it to be inflated and the SDAportion to be grouted. After inflatingthe Swellex bolt, the rock massbetween the face plate and the Swellexis pre-tensioned to the desired value.The rock mass is then exposed to con-finement pressure and the hole annu-lus grouted through the centre hole ofthe SDA. In this way, the pre-ten-sioned support element is grouted forfull protection and long lastinganchorage.

TALKING TECHNICALLY


1. The first SPEEDROD is drilled into the rock.

2. The gripers lift the second rod into place and drilling continuous.

3. When the hole is finished, the RAS system uncouples and removes the rod.

1

2

3

Mechanized Road adding RAS.

Installation sequence of the new Atlas CopcoSwellex Hybrid.

RR3/RT11 19/7/05 8:45 Page 29

Swellex® Hybrid rock bolts arerecommended for rock support in tun-nelling, civil engineering and miningapplications where active (pre-ten-sioned) support is required to preserverock mass structure, and grouting isneeded for long life expectancy. Thesystem is ideal in weak ground andaround structural discontinuities. It isalso recommended as a problem solverfor long anchorage requirements.

Swellex Hybrid

The Swellex ®Hybrid consists of aSwellex bolt coupled with one or moreMAI Self Drilling Anchors (MAISDA ®). A special connection cou-pling located between Swellex andSDA enables the Swellex bolt to beinflated and the SDA portion to begrouted.After inflating the Swellexbolt,the rock mass between the faceplate and the Swellex is pre-tensionedto the desired value.The rock mass isthen exposed to confinement pressureand the hole annulus grouted throughthe centre hole of the SDA. In this way,the pre-tensioned support element isgrouted for full protection and longlasting anchorage.

Swellex Hanger

Swellex® Pm 24H is a versatile rock-bolt having a flanged head which has afemale M30 or M36 thread. The bolt

has a static load carrying capacity of200 kN and is designed for hanging ser-vices while reinforcing the rock. Afterthe bolt has been installed by using aninflation adapter, a forged eyebolt(M30/M36) is screwed on. Utilities can

then be suspended directly from theeyebolt. The bolt, with faceplate,becomes part of the rock support pat-tern, with all the advantages of Swellex.

Swellex® Pm 24H hanger rockboltsare recommended for rock support intunnelling, civil engineering andmining applications where suspendingutilities in an underground excavationis needed. The bolts are designed asanchor points for hanging utility pipes,ventilation columns and rails, while atthe same time reinforcing the rock.Cables can also be passed through theeyebolts to form lacing or trusses inrockburst prone ground, or to reinforcefriable or weak formations. Swellex®Pm 24H can be installed using a stan-dard Swellex pump combined with aninflation adapter.

Self Drilling AnchorsSystemIn 2002, Atlas Copco incorporated theMAI series of rock bolts into its prod-uct range. Products like MAI SelfDrilling Anchors (SDA) can be used inground formations that are so soft,

TALKING TECHNICALLY


Atlas Copco SDA system is built around the Boomer, with add-on standard options, and backed up by AtlasCopco worldwide presence, know how and support.

Composition of the Atlas Copco Self Drilling Anchor (SDA).

New Swellex PM24 Hanger rockbolt.

RR3/RT11 19/7/05 8:45 Page 30

fractured, or weak that a normal drillhole will collapse before a standardrock bolt can be inserted. The SDAsystem comprises standard items likethe sacrificial bit, a variety of bolt sec-tions, couplings, faceplate and spheri-cal nut. Atlas Copco has developedsome components and functions for theRocket Boomer to make it the perfecttool for installing SDA. The standardfeed on the Boomer should be equippedwith the new BSH 110 drill steel sup-port. This is used to guide the boltwhen drilling, and when extending theSDA bolt sections. The new BSH 110is designed to leave a minimum of thebolt protruding from the rock face, thusutilizing the full length of the installedbolts. The BSH 110 has remote-con-trolled functions for guiding, grippingand drilling, giving the operator fullcontrol of the bolting sequence fromthe drilling position. The BSH 110 isfully compatible with any BMH 6000feed. For those worksites where a lot ofSDA drilling will be done, the COP1238 or COP 1838 rock drills can befitted with a special SDA shank adapterand a conversion kit. The SDA shankadapter has a female end to eliminatethe need for a loose coupling sleeve,saving time when unthreading the bolt.This makes handling easier whenextending the SDA bolts, boosting pro-ductivity and improving safety. Atwork sites where SDAs are not in dailyuse, a suitable solution is to use a shankconnector to simplify the handling of

SDAs on a standard Boomer. Theshank connector is added to the shankadapter on the hammer, and should bechosen to match the thread that is usedon the SDA. Most frequently usedthreads are R32 and R38, but also com-binations for the R51 and T76 SDAsystems are available. Once the SDAactivity is finished, the shank connectoris removed and normal drilling canresume.

BSH 110

The BSH 110 is a hydraulic drill steelsupport providing gripping and guid-ing functions. The BSH has to beequipped with the rubber bushing andsteel bushing halves to match the SDAdimension.

The standard BSH 110 will manageanchors up to size R51. There is also aspecial version, BSH 110 available forSDA installation, which minimizes thepart of the bolt protruding from therock and can fit SDA bars up to thedimension of T76. All versions ofBSH 110 have to be equipped withspecial SDA bushing halves whenhandling SDA.

Installing SDA

Most current rockbolt installationmethods are manual. However, whenthe operation is assisted by a RocketBoomer, productivity and safety aregreatly improved. Using the optionalequipment available for the standardBoomer, a typical SDA bolting semi-mechanized sequence will be as follows.

1) Modify the rock drill by attach-ing a suitable SDA shank adapter and

TALKING TECHNICALLY


Atlas Copco semi-mechanized MAI bolt installation from a Rocket Boomer.

SDA length outside tunnel face = 405

COP 1838565

256

BSH 110SDA

COP 1838

BSH 110B

SDA length outside tunnel face = 281

COP 1838565

301

Length of anchor protruding after installation, depending on BSH 110 used.

RR3/RT11 19/7/05 8:45 Page 31

TALKING TECHNICALLY


an SDA COP kit that match the threadon the MAI SDA bolt.

2) Place the MAI bolt section on thefeed with the selected MAI bit, andthread the bolt into the shank adapterfemale end. The BSH 110-SDA shouldbe in position to guide the bolt.

3) Start drilling, and adjust the pres-sure to match the chosen bolt type andthe prevailing ground conditions.Normally, the percussion pressure forSDA drilling is less than half, some-times only one third, of the hydraulicpressure set for blast hole drilling. TheSDA shank adapter makes it possibleto drill the bolt close to the tunnel wall.

4) Grip the bolt with the BSH, andhold it in position while adding anoth-er MAI bolt section, prepared with asuitable anchor coupling.

5) Once the MAI bolt section isconnected, open the BSH and contin-ue drilling. When the last section ofthe MAI bolt is being drilled, the BSH110-SDA should be fully opened, toallow the shank adapter to drill theMAI bolt deep enough to leave about280 mm of the bolt protruding.

Grouting SDA

The installation sequences describedabove use water flushing for drilling.The commonly used method for MAIbolts is post grouting. This is carriedout manually from the Boomer basket,or any other service platform, byconnecting a grouting unit to theprotruding end of the MAI bolt.

Suitable and flexible grouting unitsare the MAI M400 grout pump, andthe Atlas Copco Craelius UNI-GROUT E 22. The grout is pumpedinto the hollow MAI bolt, and is dis-tributed through the MAI drill bit into

the drilled hole, filling cavities andcracks along the bolt. This complete-ly fills the hole, forming a strongadhesion between the MAI bolt, thecured grout, and the surroundingground formation. Once the grout hascured for 8-12 h, the MAI bolt can bepost-tensioned to the required torque.

However, MAI bolt installation canalso be undertaken with continuousgrouting, using a grout pump m400NTand the new integrated injectionadapter - Ceminject.

There is usually a need to alter-nate between flushing with waterand grout. In underground installa-tion, especially for radial bolting, itmay be inconvenient to do thegrouting during drilling as this maycreate a mess of grout on the feed,and make it difficult to removeexcess grout mix used for flushing.

The alternative method offered by theCeminject system is to flush the bore-hole with water while drilling the SDA,and to commence grouting only afterreaching the design depth, while main-taining a slow rotation mode of the boltstill fixed to the drifter. This ensuresgood in-situ mixing and penetration ofthe grout around the bolt, optimizes thefriction contact with the rock/soil, andreduces wastage of grout mix.

by Olle Karlsson

Two-man operation for simultaneous drilling and grouting of SDA using a Rocket Boomer and MAI m400NTgrout pump.

Installation of anchor system using a RotaryInjection Adapter.

MAI m400NT grout pump.

RR3/RT11 19/7/05 8:45 Page 32

TALKING TECHNICALLY


Market Study

The following conclusions resultedfrom a market study performed in1995 in Canada on 71 responses from109 underground mines, some 68 ofwhich are mining metal and industrialminerals, excluding potash and salt.

The most-used mining methodreported was longhole stoping, fol-lowed by Vertical Crater Retreat, Sub-Level Caving and Cut & Fill.

An estimated 870,000 m of cablebolts are installed every year inCanada’s hard rock mines. Most minesusing cable bolts range in outputbetween 1,000 t/day and 5,000 t/day.The average total cost of drilling andinstalling the cable bolts was reportedat C$23.00 ± C$6.60/m. However,

total cost ranged between C$13/m andC$35/m, a high standard deviation thatcan be explained by disparities in thecosting systems across the samplemines.

The market for very long cablebolts is not targeted, as longer boltsare usually installed by mechanizedmeans. However, while the time

saving is sizeable with long cablebolts, it is not appreciable with lengthsof less than 8 m-10 m, when Mn24Cbecomes a good alternative.

Time is Money

A comparison has been made fortypical underground mining practices,

Swellex Mn24C threaded connection was launched in 2003.

Installing Connectable Swellex into a pilot drive.

Connectable SwellexAlternative toCable BoltsThe Mn24C connectable rock boltis a relatively new addition to theSwellex family. With a profilemade of Mn24 tubing, the sec-tions of Mn24C are coupledtogether with threaded connec-tions that can support loads atleast as high as the profilestrength. Through an ingeniousassembly, the Mn24C combinesthe exceptional ease of installa-tion of Swellex with the lengthcapability of coupled bars orcable bolts. Advantages ofMn24C rockbolts are ease andspeed of installation, and qualityassurance of installation and per-formance. Many mine operatorsalready consider ConnectableSwellex Mn24 to be the bestsolution to their ground controlproblems in stoping. Althoughmanual installation does notappear attractive on a large scale,operators are extremely interest-ed in replacing their time con-suming cable bolting operationswith the simpler and safer Swellexsystem. With a semi-mechanizedinstallation, Connectable Swellexis very competitive, and isdeemed profitable in both NorthAmerica and South America.

RR3_RT12.qxd 23/6/05 10:04 Page 33

TALKING TECHNICALLY


installing manual or semi-mechanizedcable bolts, using a 40 double strandcable bolts block or a 60 single strandcable bolts block. It was assumed thatthe support capacity required by thedesigned pattern of double strandcable bolts would be met by an arrayof 60 Mn24C rockbolts. The costanalysis presented in Table 1 showsthat, in a semi-mechanized installa-tion, using Mn24C rockbolts toreplace short cable bolts of less than 8 m-long saves a good deal of time. Inaddition, quality control is better, andtraining is very simple. Analysis ofTable 1 shows also that, for an Mn24Cprice of C$16.50/m for the bolts, thecombined system would have an

operating marginal cost similar to cablebolts. Increase in productivity still hasto be analyzed in term of costs saving.

Conclusion

Productivity and costs analyses havealso been carried out to assess thecompetitiveness of the Mn24C rock-bolts with cable bolting.

Field testing in Canadian minesdemonstrated higher productivity inore extraction and development, dueto the flexibility of installation of theMn24C bolts. Perfect installation bynon-specialized crews, with immedi-ate support over the entire length ofthe bolt, contributed to a higher

efficiency. Quality of installation wasnot jeopardized by geological crackingand voids, or water, and there was nowait for curing before tensioning.

The increase in productivity can beutilized to accelerate development ofstopes, adding flexibility to mine plan-ning, and facilitating the timelyextraction of ore and its delivery to themill. The added productivity wouldalso mean less overtime and schedul-ing conflicts.

To summarize, Mn24C is not only avery efficient means of ground sup-port, it also underpins a smoothmining operation.

by François Charette

Table 1. Comparison of typical installation performances for Cable bolts and Mn24C.

Cable Bolts Cable Bolts Mn24C Mn24C Mn24CManual Manual Manual Semi-Mechanized Semi-Mechanized

Installation Installation Installation Installation InstallationDrilling – Installation Simultaneous

Separate Installation

Calculation Base: Calculation Base: Calculation Base: Calculation Base: Calculation Base: 40 double Cable 60 single Cable 60 Connectables 60 Connectables 60 Connectables bolts 6 m long bolts 6 m long 6 m long 6 m long 6 m long

Drilling (Long Hole): Drilling (Long Hole): Drilling (Long Hole): Drilling (Long Hole): Drilling (Long Hole): 1.3 shifts x 1 man 1.4 shifts x 1 man 1.4 shifts x 1 man 1.4 shifts x 1 man 1.4 shifts x 1 man64 mm diameter 50 mm diameter 50 mm diameter 50 mm diameter 50 mm diameter

holes holes holes holes holes

Installation: Installation: Installation: Installation: Installation: 2 shift x 2 men 3 shift x 2 men 2.3 shift x 2 men 2.3 shift x 1 man 1.4 shift x 1 man

Grouting: Grouting: Details: installation Details: installation 1.25 shift x 2 men 2.6 shift x 2 men time is 10 min. time is 10 min.

and is performed after and can be performedall the holes are drilled. between each

hole drilled.

Plate tensioning: Plate tensioning: 0.5 shift x 2 men 0.5 shift x 2 men

Total: 9.8 man-shifts Total: 13.6 man-shifts Total: 6.0 man-shifts Total: 3.7 man-shifts Total: 2.8 man-shifts

Elapsed time: Elapsed time: Elapsed time: Elapsed time: Elapsed time: 5.0 shifts 6.0 shifts 3.7 shifts 3.7 shifts 2.8 shifts

Supplies: cables, Supplies: cables, Supplies: Supplies: Supplies:grout tube, grout, grout tube, grout, Connectables, Connectables, Connectables,plate, barrel and plate, barrel and retainers, plate and retainers, plate and retainers, plate and

wedge wedge $0.50/m for seals $0.50/m for seals $0.50/m for sealsand pumps parts and pumps parts and pumps parts

Drilling costs: Drilling costs: Drilling costs: Drilling costs: Drilling costs: $5.80/m $5.00/m $5.00/m $5.00/m $ 5.00/m

Supplies cost: Supplies cost: Supplies cost: Supplies cost: Supplies cost: $8.50/m $6.40/m $17.00/m $17.00/m $ 17.00/mInstall.: Install.: Install.: Install.: Install.:

$11.20/m ($45/h) $12.20/m ($45/h) $4.60/m ($45/h) $2.30/m ($45/h) $1.40/m ($45/h)

Total: $25.50/m Total: $23.60/m Total: $26.70/m Total: $24.40/m Total: $23.40/m

RR3_RT12.qxd 23/6/05 10:04 Page 34

TALKING TECHNICALLY


Corrosion Underground

Corrosion can be either uniform on theexposed steel surface, or very localized.Uniform corrosion is characterized by aregular loss of metal from the corrod-ing surface, while localized corrosionwill produce metal loss in a very con-fined area of the exposed surface.

Under uniform corrosion, a rock-bolt will be radially thinned from theoutside or the inside, or, in the case ofsplit tube stabilizers, from both sides.Localized corrosion by pitting can beseen in areas where the bolt surface is

metallurgically non-homogenous, orwhere certain types of rock mineralsare in contact with the bolt. Crevicecorrosion can occur with confined andclosely spaced metal surfaces, such asat the interface between bolt collar andface plate. It has also been observedthat, in highly corrosive environments,uniform and localized corrosion canoccur simultaneously.

Galvanic corrosion is another typeof corrosion where dissimilar metalsare in contact in the presence of anelectrolyte, either liquid water orvapour. A more appropriate descrip-tion may be bimetallic corrosion.

Graphical representation of thetypes of corrosion likely to attackrockbolts is presented in Figure 2,modified after Dillon (1982).

In the main, environmental factorswill determine the type of corrosion andthe mode of attack. From the point ofview of mechanism of attack, there aretwo main modes of attack in under-ground environments: corrosion inwater, where the bolts are in contactwith running water; and atmospheric

corrosion, where aggressive airbornecontaminants are deposited on rockboltsand any metallic surfaces. Water inflow,chemicals in water, microbial species,and fumes from both diesel engineexhausts and explosive blasts, are themost common factors that will impacton the corrosion rate of rockbolts. Levelof isolation from external agents willalso determine the rate of corrosion.

The major blame for corrosion inwater lies with chloride and sulphateions. Very high concentrations of theseions have been measured in both civilengineering and mine tunnels, all overthe world. Iron sulphide minerals,principally pyrite and chalcopyrite, arepresent in most metal mines, whereasan extremely high chloride andsulphate ions concentration is moretypical of Australian mines. Oxidationof pyrite produces sulphuric acid, andmine waters with pH as low as 2 canbe produced. Also, water flow, andchanges in ions concentration overtime, will affect passivation. Use of re-circulated water increases the potentialfor corrosion problems.

Figure 1. Pull testing to verify long term mechanical properties of Swellex rockbolt.

Rockbolt Corrosion in Miningand TunnellingObserving CorrosionThe phenomenon of corrosion ofrockbolts in an undergroundenvironment is a subject that isattracting more and more atten-tion from engineers and projectowners. Field observations haveshown that, in some conditions,unprotected rockbolts corrodefreely and rapidly. A closer lookat the overall conditions at moni-tored sites highlights the diffi-culty in predicting the life of thebolts. Often, water conditions arenot taken into account. Althoughwater supply can be non-corro-sive at source, the process of re-circulating water often gatherscorrosive ions, and renders thewater more aggressive towardsteel components.

At Atlas Copco, it was recog-nized that theoretical predictionsof a rockbolt’s life could only be afirst assessment of applicabilityof non-protected ground support.Ultimately, extra protection isneeded to isolate the rockboltfrom an aggressive environment.This can increase the effective lifeof the ground support, and secureits long-term performance.

Observed field performance inknown conditions can provide anextremely instructive insight ofthe global corrosion process, andon the means to alleviate itseffect on ground support.

RR3/RT13.qxd 23/6/05 10:05 Page 35

Corrosion Potential

Queries about the life expectancy ofrockbolts are frequently received byAtlas Copco from its customers.While the only way to assure long-lifeperformance under aggressive condi-tions is to coat the bolt to isolate itfrom the environment, the need toknow the expected life span in tempo-rary bolting applications has stimulat-ed research and development in theRock Reinforcement group. A newapproach was elaborated, consisting ofthree steps that allow a high level ofcontrol on the bolt’s performance.

First, preliminary analysis of corro-sion potential is carried out, usingfield data and standards in the field of

corrosion, such as DIN 50 929. Thisfirst step allows the tunnel owner, ormine operator, to make a first decisionon the need for corrosion protection.Next, during the operation of thetunnel or mine, regular testing can beperformed, in order to assess the realcorrosion rate of the rock support.Third, if the tests showed that theenvironment is corrosive enough toreduce the effective life below thatrequired by the customer, the use of acorrosion protected Coated Swellex isrecommended.

Table 1 presents theoretical corro-sion rates calculated with the normDIN 50 929 for underground sites inSweden, Japan, Canada and Australia.Typical tests performed include water

analysis, destructive pull tests andprofile endoscopy with a fibre opticsborehole camera (Figure 3). Figures 4and 5 show the interior profile for twoSwellex bolts, corroded and non-cor-roded. Pull tests, performed with theequipment shown in Figure 1, willprovide an index of load capacity atthe collar of the bolt. It has beenobserved with the borehole camerathat corrosion is limited to the first 30cm from the inflation bushing, so theloading capacity of the bolt inside therock mass is almost always kept aboveits rated value. In relatively non-aggressive environments, non-coatedSwellex bolts have proved to retaintheir minimum loading capacity forover 10 years.

Corrosion Protection

Atlas Copco Coated bolts are coveredwith Corrolastic Expander Paint839BX. This paint has been tested by

TALKING TECHNICALLY


Figure 2. Types of corrosion encountered on rockbolts (from Dillon 1992).

Figure 3. Fibre optics borehole endoscopic camera.

Figure 4. Snapshot of inside view of Swellex bolt with borehole camera – nocorrosion visible inside the Swellex profile.

Figure 5. Snapshot of inside view of Swellex bolt with borehole camera –corrosion visible inside the Swellex profile.

RR3/RT13.qxd 23/6/05 10:05 Page 36

the Swedish Corrosion Institute inextremely aggressive environments,and proved not to be affected by highchloride or sulphuric acid levels forperiods over 10 years. In Table 1, theSwedish Corrosion Institute has assessedthat the life span (at Aspo) of a CoatedSwellex in a very aggressive environ-ment would be of more than 20 years.The most critical parameters in corro-sion protection are the characteristiccorrosion sensibility of the coating, andthe physical state of the coating withreference to scratches and indentations.

Tests performed by the SwedishCorrosion Institute for Swelleximmersed in sulphuric acid haveshown that, while the corrosion rate of unprotected Swellex would be0.5 mm/year in the simulated environ-ment, the Coated Swellex showed notraces of general corrosion, and pittingat scratch locations stayed very local-ized. In these conditions, corrosion inunprotected areas would not migrateto a protected area, the coating mini-mizing corrosion and controlling itsspread.

It has been demonstrated that corro-sion is a very complex process, andcorrosion rates are very hard to predict

accurately. However, predictive meth-ods can be helpful to evaluate the needfor corrosion protected rockbolts.Field observations, followed by pro-tective coating of the rockbolt wherenecessary, can be used to control cor-rosion, both in temporary and perma-nent rock reinforcement applications.This approach to corrosion of rock-bolts has been developed by AtlasCopco to deal with the need for lifeexpectancy assessment in the miningand construction industries.

Case Study at Aspo

The 4 km-long subsea tunnel driven toaccess the site of the Aspo nuclearwaste research laboratory atOskarshamn, Sweden required somerock reinforcement, despite high quali-ty rock over most of its length. Inareas requiring support, rockbolts,rockbolts with wire mesh, and rock-bolts with wire mesh and steel fibrereinforced shotcrete were used. Testdrilling showed that rock reinforce-ment would get more difficult as thetunnel progressed, because fissurezones and saltwater leakage wouldplace high demands on holding power

and corrosion resistance. At a depth of300 m, the sodium chloride content ofthe seawater increases dramatically to1.5%.

Sydkraft Konsult chose Swellex forthe job, because of their high degreeof versatility and quality of installa-tion. The corrosion protection onCoated Swellex met their demands forlong duration use, and they found thequick and simple installation, with fullsupport over the entire length of thebolt, extremely reassuring. Short 90 cm Swellex bolts were used for netfixing, and 2.4 m-long Swellex boltswere used for the main rock reinforce-ment duties.

The views of the project manage-ment were borne out by a study car-ried out by the Swedish CorrosionInstitute to estimate the risk of corro-sion of Swellex rock bolts used atAspo laboratory, from which the fol-lowing conclusions were made.

Bolts with an intact corrosion pro-tection layer are not attacked for manyyears. In places where the layer isdamaged, there is a risk for general aswell as local corrosion. The attackwill, however, be limited and, as such,less significant for the strength of thebolt. The time for fracture due to gen-eral corrosion for a 2 mm-thick boltcan be considerably longer than 20years, mainly due to low oxygen con-tent in the water. The attack will, how-ever, be limited and, as such, be lesssignificant for the strength of the bolt.


TALKING TECHNICALLY


CORROSION POTENTIAL ASSESSMENT STEPS

1. PRELIMINARY ANALYSIS USING DIN 50 929

2. FOLLOW UP OF PERFORMANCE OF ROCKBOLTS – CAPACITYMEASUREMENT – ENDOSCOPY – WATER ANALYSIS TO MONITORCHANGES IN CONDITIONS

3. RE-ASSESSMENT OF ADEQUACY OF CORROSION RESISTANCETOOLS: WATER ANALYSIS, PULL TESTING, BOREHOLE CAMERA

Table 1. Corrosion Rate Assessment of Unprotected Steel for Underground Sites Using DIN 59 929

Sites Ca (mg/l) Cl (mg/l) SO4 (mg/l) HCO3 (mg/l) pH Assessed Corrosion RateGerman DIN 50 929 forUniform/Pitting (mm/year)

Mine A Canada 600 540 1610 NA 7.8 0.1/0.5

Mine B Canada 540 870 61700 NA 3.4 More than 0.1/0.5

Kapuzineberg Sweden 22 2661 1.3 NA 6.95 0.1/0.5

Ritto Japan 13 2 3 52 6.7 0.1/0.5

Aspo Sweden N/A N/A N/A N/A N/A 0.1/0.5 for non-coated0.02/0.1 for Coated Swellex

Mine C Australia 140 1200 420 100 7.9 0.05/0.2

Mine D Australia 350 10 8300 38 3.0 0.1/0.5

RR3/RT13.qxd 23/6/05 10:05 Page 37

TALKING TECHNICALLY


Drilling for Grouting inTunnelsGrouting is often considered as a hin-drance in the progress of the tunneladvance. Instead it should be seen as atool for the next step, and as one of themost important parts of the final rocksupport.

The intention is to use the cementto stabilize, strengthen or seal theground mass around the tunnel. It is awaste of time and money to blast andexcavate the rock far outside therequired profile, and then replaceoverbreak with concrete.

Grout holes for pregrouting in tun-nels are 15-25 m-long, and should end3-4 m outside the theoretical contour,

and with a maximum deviation of 3-5% from the intended target. Thisinvolves starting with guide rods, andthen using a rod adding system. Biggerrod sizes are needed to ensure betterstability compared to blast hole drilling.The diameter is normally 51-64 mm.

When the ground is of poor quality,it is harder to drill the holes, and theneed to drill straight holes is muchgreater. In such ground it is alsoessential to place the grout where it isrequired.

Where possible, grout holes shouldbe drilled at right angles to the mainfissures, in order to intercept as manyas possible. This is important whenpost-grouting in tunnels, as well as intraditional surface grouting.

Cycle of events in face excavation and support.

Grouting for Support in TunnelsEighty Years ofDevelopmentAtlas Copco Craelius has beenactive within the area of groutingfor over 80 years. The companyoriginally started to develop andmanufacture grouting equipmentin an attempt to rescue expensiveholes. These generally occurredwhen entering poor, fracturedrock, in which the drill stringshowed signs of getting stuck, orflushing fluids were lost.

Later on, grouting tools wouldaccompany Atlas Copco Craeliusdiamond drilling equipment onlarge international tunnellingprojects.

Today, grouting encompassesso much more than traditionalground injection in tunnels,although it is still generallydefined as an injection underpressure of fluid material intofractures and cavities in rock, soilor artificial structures. Dependingon the composition and mix ofthe injected material, it will reactphysically and chemically to sta-bilize, strengthen, or seal theground or the structure. InScandinavia, the lower cost oftunnels compared to the rest ofEurope is not only due to betterrock quality, but also becausegrouting is classified as part ofthe support.

It is generally accepted thathigh grouting pressure, developedprimarily by the French for use inthe Alps, increases the groutedvolume and strengthens andseals planes of weakness. Bettereconomy is expected using highpressures, by way of reduceddrilling costs and a higher outputof fresh, stable grout, especiallywhen using microcements.

Low pressure grouting, devel-oped by the Americans for the sed-imentary formations in the USA,and by the British in the coalfields,is designed to avoid furtherdamage to the strata by crackingor widening existing cracks.

RR3/RT14.qxd 23/6/05 10:07 Page 38

This demand is difficult to meetwhen pre-grouting in tunnels, wherespacing is reduced to ensure thatfissure planes, with an unfavourableorientation to the grout holes, will begrouted properly. Here, the diameterof the drillhole has very limited influ-ence on the grouting result.

Because of the stiffness of the drill string, larger hole diameters ingeneral result in straighter, albeit moreexpensive, holes. The setting ofpackers is more expensive and diffi-cult in large diameter holes, as is thegrouting.

General requirements for drillingequipment in tunnelling work are asfollows. If possible, drill all holesfrom a single set up, and with two dif-ferent rod sizes and three differenthole diameters for blast hole, cut holeand grout hole. Use a service platformand a rod adding system (RAS) withrod magazine: drilling for a groutround may involve handling some 5 tof drill steel. A positioning controlinstrument is a necessity, together withgood working lights, and an elevatedsound-protected cabin for full view ofthe face. A stepless mix of flushwaterand air is advisable, bearing in mindthat one drill rig uses 200-300 lit/minof water. High pressure cleaningequipment will be necessary for thegrout holes and the drilling and grout-ing equipment.

Grouting is too often planned andcarried out as an off time shift, whenthe drilling equipment is elsewhere.Thus, when there is a need for addi-tional grout hole drilling, this cannot beundertaken immediately. Consequentlythe driller cannot easily pass hisinformation and observations to thegrouting technician.

Grouting in TunnelsTunnels are constructed for many dif-ferent purposes, and under widelyvarying geographic and geologicalconditions. Tunnels carrying fluids, beit fresh water or sewage, should notleak; and all tunnels should resist theinflow of water from the surroundingground.

The latter requirement may benecessary to avoid draining naturalwater into the tunnel, which could lead to a general lowering of theground water table in a wide areaabove its alignment. Movement of thewater table may result in subsidenceand damage to existing surface struc-tures, loss of capacity of drinkingwater wells, and similar undesirableconsequences.

In other instances, especially inunstable ground containing runningmaterial under pressure, or in karstformations, grouting may be necessaryto stabilize, strengthen and seal thestrata.

Tunnels that have to be watertight,as well as tunnels in weak ground thathave to have a long service life, areusually lined. This lining is oftenplaced concurrently with the tunnellingprocess itself, particularly in TBMbored tunnels where it is constructedof rings of prefabricated segments.

Even in bored tunnels, where theexcavated shape and diameter arecontrolled within narrow limits,there will be a slight annular gapbetween the outside of the liningand the inside of the bore. Groutingbehind the lining serves the purposeof filling this gap, so that the liningwill support the ground from thebeginning, without settlement. This

contact grouting method also servesto seal the joints between the liningsegments.

Pregrouting

The cost for pregrouting can be5-10 % of the cost of postgrouting forreaching comparable and satisfactoryresults.

The main reason is that both thegrout pressure and the grout flow canbe fully utilized in undisturbed rockwhereas postgrouting always is doneagainst a free surface, often crackedup from blasting and excavation.

Investigation drilling is done duringthe actual tunnel work and parallelwith the pregrouting in order to inves-tigate the rock properties, like cracks,fissures and fissure systems, occur-rence of water, and soft or weatheredrock, for the next 50 metres or so.Pregrouting means that the rock istreated ahead of excavation.

These two operations are repeateduntil a satisfactory result is achieved.

The pregrouted zone should alwaysgo beyond the area that is disturbed byblasting, bolting or excavation.

Grouting and pregrouting of tunnelshave three different purposes:stabilization, strengthening and seal-ing of the ground.

Stabilization grouting creates askeleton of grout in weak parts orareas of the rock, to avoid sliding incracks, fissures or bedding planes.This type of is grouting is to support atemporary construction or when a con-crete casting is done at a later stage.

Strengthening grouting is done forreinforcing a tunnel permanently. Inmost cases it is less expensive to uti-lize and strengthen the existing rockstructure compared to replacing it witha new construction of concrete.

Sealing grouting is strengtheninggrouting developed to almost watertightness. Sealing grouting is dividedinto different sealing classes depend-ing on permissible water inflow.

In Scandinavia normal tunnels aresaid to present insignificant problemswhen the leakage is in the range ofless than 5 lit/min per 100 m. Ifit exceeds 10-20 lit/min per 100 m,then significant problems will occur.

TALKING TECHNICALLY


Grouting of the curtain cone.

RR3/RT14.qxd 23/6/05 10:07 Page 39

Drammen Case StudyAt the Norwegian port of Drammen, asecond single-tube 2.3 km-long tunnelwith bi-directional traffic flow wasrequired to relieve congestion on thenorth bank of the river. The tunnel ison a curved alignment beneath theBragernes Ridge, an outcrop of igneousrock comprising 50% porphyry and50% basalt. The main face had anexcavated arched cross-section of 70.5 sq m, which included a large drain.

The main contractor was Selmer,for client Statens Vegvesen Buskerud,the local agency of the NorwegianState Highways Authority.

A condition on the construction ofthe tunnel demanded that there be nointerference with the water table, andthe tunnel itself be kept dry. The maxi-mum ingress of water allowed beforegrouting was 30 lit/min/100 m towardsthe tunnel ends, and 10 lit/min/100 min the centre section.

The grouting sequence commencedwith the drilling of 27 m-long, 51 mm-diameter holes ahead of the face to testfor water. These were drilled by anAtlas Copco Rocket Boomer 353S,using threaded extension steel, whichwas manually attached. Generally, tenforward holes were drilled, with a 10 m overlap, allowing 17 m advancebetween events.

The contract envisaged injection of2,370 t of grout to achieve the objective

water flows, a major operation forwhich Selmer invested in a sophisti-cated Atlas Copco Craelius truck-mounted Unigrout E 400-100 WB.This comprised a containerizedmixing and pumping plant with exter-nal cement feed and additive hoppers,and liquid additive tank. Inside thecontainer were two Cemag units, andtwo 400 lit/min Pumpac units, with asingle 400 litre Cemix WB weightbatching mixer. The unit’s nominalcapacity is 4 t/h of dry cement, but upto 66 t of cement was successfullyinjected into a particularly wet roundover a 15 h period.

Pumping and Logging

The Atlas Copco Craelius PumpacSystem is based on a double actingpump principle. The system has beenmade simple and user-friendly by wayof modularized parts, independent andstepless variable pressure and flow,easy and fast change of valve assem-bly units, and environmentally friend-ly hydraulic fluid. Then the whole lifecost is kept to a minimum by systemadaptability. The system features ahydraulic switch-over system, inte-grated in the hydraulic cylinder, and asplit cotter fast-locking system of thetwo piston rods for easy dismantlingof the cylinder assembly. Three sizesof electric motors are available: 7.5 kW, 15 kW and 22 kW. There are

two sizes of grout cylinders: 110 mmand 150 mm diameter; and two typesof valves: ball valves for normalgrouting applications, and disc valvesfor when a smooth flow and minimalpressure drop are required. Main-tenance is easy, by way of a selfcleaning cement fluid end, waterflushing of cement and hydraulicpiston rods, and only one 46 mmwrench for servicing the cement pump.

The Logac system is a computerbased logging system for samplingand storing of data during the groutingoperation. The recorder is housed in acabinet with a Craelius Flow Pressure(CFP) meter unit equipped with cableand quick coupling for easy connec-tion. The CFP meter unit consists ofan electromagnetic flow-meter and apressure-meter. The logged parametersare flow, pressure, volume, time, realtime and hole number. The standardflow meter operates in a range of 0-200 lit/min with a maximum pressureof 40 and 100 bar respectively. Thestandard pressure sensor covers arange of 0-100 bar. All parameters areshown in real time on the Logac 4000recorder display, and stored on a PC-card. The Logac 4000 samples data sixtimes per second, and stores it on thecard every 10th second. The card canbe kept as a permanent record forfuture references, or reused over andover again. The control panel consistsof an on/off switch for the recorder, adisplay, a separate button for each ofthe eight groutlines, and a 10-keykeypad. Each groutline shows time,real time, flow, pressure and volume.There is a button to show either onesingle line, or all eight lines simultane-ously, and two diodes, one for tellingwhen logging is on, and the other forinforming when the memory card is90% full.

One reason for Selmer’s success atDrammen was that they could continu-ously pump high volumes of stablegrout at high pressures. A normalpumping rate is 110-120 lit/min at 50-60 bar, and they used 80 bar as stopcriterion, and sometimes even 90 bar.The water/cement ratio ranged from1.0 to 0.5.

by Sten-Äke Pettersson

TALKING TECHNICALLY


Container mounted grout mixing and injection system to be carried on a truck.

RR3/RT14.qxd 23/6/05 10:07 Page 40

TALKING TECHNICALLY


Tomei Study

In a study on the Tomei tunnel inJapan, the influence on support of therockbolt installation method wasinvestigated by means of numericalmodelling.

It was found that the Swellex rock-bolt exhibits more support effect right

after installation, and also has greatercontrol effect of displacement androck mass plasticity, compared togrouted rockbolts. For stabilization ofthe region up to about 0.5D behind the face, the Swellex rockbolt is amore effective device than the groutedrockbolt.

The Swellex rockbolt also has morecontrol over the shear behaviour ofjoints compared to the grouted rock-bolt, because Swellex exhibits supportfaster. As a result, it contributes to theformation of the natural arch, byimproving stress continuity around thetunnel, as well as displacement con-trol. Because one of the main roles ofthe rockbolt is to improve discontinu-ous rock mass to continuum, it can be

said that the Swellex rockbolt is verysuitable for support of a discontinuousrock mass.

Comparisons between 4 m and 6 mlengths of Swellex were also carriedout. No difference in support effectbetween the two lengths was found,offering the possibility of shorter boltlengths if Swellex is used. This isbecause Swellex completes the naturalarch immediately after installation.

Numerical Modelling

Face stabilization methods usingSwellex at Tomei were also confirmedby means of numerical modelling.

Tests determined the bonding stiff-ness and bond strength of Swellex and

Pull-out testing of rockbolts in the underground laboratory.

Rock Mass Stability withSwellexEarly StrengthMeans EarlySupportAccording to Konda and Itoh, therock mass in a tunnel is unstablebetween the face and 0.5Dbehind the face, regardless ofrock types. Collapses occur mostoften when the stress/strengthratio of rock mass is smaller than5, especially in sedimentary rock.Discontinuities, caused by jointsin the harder igneous and meta-morphic rocks, have also resultedin rock falls up to 0.5D behind theface. The risk of collapse in thisarea grows with increasing crosssection of the tunnel.

Steel Fibre Reinforced Shot-crete (SFRS) was recommendedto increase the rock stability inthe Tomei tunnel. The 28-daystrength of this shotcrete was36N/mm2, using a steel fibremixture ratio of 0.7%. However,early strength would be requiredto give the necessary support.Unfortunately, attempts to in-crease the early strength ofshotcrete may induce micro-cracking, with negative effect on the long-term stability of the concrete, particularly wherethe initial deformation speed of the rock is high.

Without early shotcretestrength, rockbolts become themain support. However, sincestandard rockbolt groutingmaterials require time to harden,they don’t have much effect onthe initial stability of the rockmass.

RR3/RT15.qxd 23/6/05 10:09 Page 41

grouted rockbolts as input for numeri-cal modelling. Using these values,two-dimension and three-dimensionmodels simulated pull-out tests.

The rockbolt axial force generatedat the tunnel crown in the case ofgrouted rockbolts was 1 kN immedi-ately after installation, rising to 32 kNmaximum. In the case of Swellex, 30 kN was generated immediately,rising to 38 kN. For Swellex, the axialforce is more than 60% of the maxi-mum value from the beginning, and isabout 1.6 times that of grouted rock-bolts.

Overall distribution of rockboltaxial force was measured at 1 m, 10 m, 20 m, and 30 m behind the face.

Using grouted rockbolts, almost noaxial force was generated from crownto sidewall immediately behind theface. At 10 m (0.5D) behind the face,30 kN was generated at the crown and 82 kN at the sidewall. UsingSwellex, 33 kN was generated at thecrown, and 66 kN at the sidewall right

behind the face. At 10 m behind theface, 50 kN was generated at thecrown and 131 kN at the sidewall.

For both cases, loads on rockboltsdo not increase more than 1D behindthe face, due to the convergence ten-dency of rock mass displacement.Except for right after installation, axialforce generated is about 1.5 timeslarger for Swellex than for grouted.

Natural Arch

The difference of crown settlementsfor grouted bolts and Swellex was 0.5 mm, 1.2 mm, and 1.5 mm at 1 m,10 m, and 20 m behind the face,respectively.

Using grouted bolts, a plasticregion of about 4 m is generated fromthe crown to the sidewall section. Inthe case of Swellex, the plastic regionnear the crown tends to decrease, andthe value is controlled at about 2 m.Where there is no support, the value is6 m at the crown, and 4 m at the sidewall section.

The tunnel is stabilized by generat-ing a natural arch of the surroundingrock mass, preserving its continuityfor tangential stress. In the case of theSwellex rockbolt, since the continuityfor ground stress of the arch section isgreater than when using grouted rock-bolts, it is thought to have a majoreffect on tunnel stabilization.

Joint shear displacement is generatedwithin 4.0 m of the tunnel profile, andthis can be controlled immediatelyusing a 4 m-long Swellex bolt. Withgrouted rockbolts, shear displacement

extends to more than 4 m, due to thetime lapse for grout hardening.

When using Swellex rock bolts,maximum bonding with the strata isachieved right after installation, so therequired bolt length is shorter thanwith grouted bolts.

Summary

The excellent support effect ofSwellex rockbolts can be summarizedin four points as follows.

Compared with grouted rockbolts,Swellex exhibits a much greater sup-port effect right after installation, andcontributes to stabilization of the rockmass near to the face. In a continuousrock mass, Swellex has a greater con-trol effect over the plastic region. Inheavily jointed rock, Swellex con-tributes more to the formation of thenatural arch by controlling the shearbehaviour of joints, improving thestress continuity of the rock mass.Swellex controls tunnel deformationbetter, and exhibits excellent support,making it superior to the equivalentgrouted rockbolt.

Because stabilization of the rockmass close to the face was a key pointfor the Tomei tunnel, Swellex rock-bolts were specified. Swellex enablesa tunnel structure to be stabilized bysupport, without the impediment ofcuring time for shotcrete and groutingmaterials. By installing Swellex boltsimmediately after excavation, it ispossible to avoid rock instability.

by Federico Scolari

TALKING TECHNICALLY


Laboratory testing has determined the relationshipbetween curing time and load capacity for groutedrebars.

Displacement contour, rockbolt axial force, longitudinal, for grouted rebars. Displacement contour, using shorter Swellex rockbolts.

RR3/RT15.qxd 23/6/05 10:09 Page 42

Tough Rods for a Tough Life

Rods have a tough life, transferring thepercussion energy from rock drill tobit, and then into the rock. They’realso subjected to high bending stress,not to mention corrosive water in theflushing hole. These harsh facts havenot only guided Atlas Copco Secorocin its selection of steel quality, manu-facturing technique and heat treatmentprocesses, but also in their decision tohave a rolled-in stainless liningthroughout the entire length of theflushing hole. Even the drifted flushinghole at the shank end is lined in thesame way. The flushing hole is alsoprotected by special anti-corrosion oilas standard, to prevent corrosion andrisk of rod breakage. And for evengreater protection, Uppercut rods havesurface hardened shank and taperedsections for high wear resistance onthose parts exposed to severe stressesduring drilling.

Secoroc tapered rods are alreadyrenowned for their superior fatigue

strength and resistance to bendingstress, and, with the Uppercut range,have improved material properties stillfurther.

Question of Degrees

Different taper angles are used for dif-ferent rock formations and rock drills.A wide taper angle is normally usedwhen drilling with high impacthydraulic rock drills in medium hardto hard and abrasive rock formations.Taper angles of 11 degrees and 12degrees are common on modern rigs.

A narrow taper angle of 7 degrees isused for low impact rock drills andsofter rock formations. This angle canalso be used to counter spinning prob-lems when using 11 degrees or 12degrees equipment. In addition, a 4degrees 46 minutes angle is available forvery soft rock, to prevent bits from spin-ning or becoming detached when usingpneumatic or hydraulic rock drills.

Secoroc Uppercut rods are availablewith 22 mm hexagonal rod section and

TALKING TECHNICALLY


Secoroc Uppercut – HighQuality Tapered EquipmentDesigned forPressureIncreasingly powerful pneumaticand hydraulic rock drills placegreat demands on rock drillingtools, a fact that is well known todrillers working in mining anddimensional stone applications.This is the reality that has guidedAtlas Copco Secoroc in thedesign of its range of Uppercuttapered equipment.

At the heart of these innova-tive products there is a formid-able steel grade and specializedmanufacturing technique. Theunique heat treatment processemployed helps to release theinternal stresses of the steel andgive it greater bending resis-tance, while retaining high dura-bility. The result is a tapered rodthat’s better suited to the stress-es and strains of modern rockdrills.

All in all, you won’t find longer lasting rods on the markettoday!

Features of Secoroc Uppercut tapered rod.

RR3/RT16 23/6/05 10:10 Page 43

shank length 108 mm for 4 degree 46minute, 7 degree, 11 degree and 12degree tapers. Uppercut rods with 25mm hexagonal rod section and shanklength 159 mm are available with 12degree taper.

High Performance Bits

Secoroc bit design and productionprocesses are in a state of constantrefinement. The Secoroc Uppercut

range comprises button and cross-typebits in an extensive selection of designconfigurations. These designs can beused in a variety of rock formationsfor maximum productivity.

Moreover, there are two newmodels, with an extra front button forimproved hole straightness, higherpenetration rate and longer servicelife. Furthermore, the Secoroc range ofballistic button bits is in the process ofbeing extended to meet ever morediverse demands.

Prepared for the Future

Secoroc Uppercut tapered equipmentcan be used in all types of applicationsand rock formations. The lowestcost/metre drilled, a claim that haslong been synonymous with Secorocproducts, is now lower than ever withthis range, along with higher drillingproductivity.

Tapered products, which first appearedon the scene in the 1960s, can readily handle the impact energy frommodern pneumatic and hydraulic rockdrills, while they are also ready to cope withthe stronger rock drills currently on thedrawing board.

Nowadays, tapered equipment isfavoured for increased penetrationrate, longer service life and lower

drilling costs, and is taking marketshare from integrals, especially inmining applications and the dimen-sional stone industry.

by Jan Lindkvist

TALKING TECHNICALLY


Range of Uppercut tapered rods and bits from Atlas Copco Secoroc.

The Secoroc UppercutRod

● Special anti-corrosion oil toprotect the flushing hole ofthe rod

● Surface hardened taperend for high wearresistance and a longerservice life

● Stainless steel flushingtube lining to preventcorrosion and breakage

● Drifted flushing hole withstainless steel lining at theshank end preventsbreakage and increasesservice life

● Surface hardened shankend for high wearresistance and a longerservice life

● Z708 steel for superiorfatigue and bendingstrength

Uppercut tapered rod and button bit ready to drill.

RR3/RT16 23/6/05 10:10 Page 44

Thread of Innovation

To solve the problem, Atlas CopcoSecoroc faced two choices: eitherincrease the dimensions of the rodsand bits in the same way as everybodyelse, or find a new way. Being notori-ously stubborn innovators, the choicewas easy.

During the creative process, threeimportant insights emerged. First, thehole sizes should remain as for drillingwith standard equipment. Second, thebits should be easy to uncouple. Andthird, the old thread design had to beleft behind.

As with all genuinely groundbreak-ing endeavours, the solution wasdeceptively simple. The secret of theMagnum SR thread design is that the

diameter is larger at the end of thethread and smaller at its tip. By addingconsiderably more steel at the end ofthe thread, the new design was given adistinctive, conical shape. This con-cept not only upped the fatigue resis-tance of the rods, but also reduced thetendency to deviate during collaring.

The Magnum SR thread design alsohas the added bonus that the bits arevery easy to uncouple and change,saving time and equipment, and result-ing in more holes drilled. Magnum SRhas proved a big hit with operators.

The new Magnum SR system for drift-ing and rockbolting, specially designedfor the new generation of powerful drill-rigs, delivers more and straighter holesper shift and has a considerably longerservice life than any competing system.

Field Tests Worldwide

Extensive field tests with the MagnumSR were carried out on four conti-nents, and involved more than a halfmillion metres of drilling over aperiod of one year.

TALKING TECHNICALLY


Magnum SR used in a bolting application.

Speedy Rock ReinforcementUsing Magnum SRThread System forthe FutureThe tried and tested thread sys-tems, R25, R28 and R32, haveserved underground drillers wellfor many years. However, withthe introduction of ever-morepowerful hydraulic rigs, thesebattle-worn solutions started toshow weakness. Rod breakage atthe bit end, either just behind theskirt or on the last thread, wasbecoming distressingly common.Why? Because it’s the most vul-nerable part of the rod.Consequently, bits were lost,leading to costly downtime. Evenworse, holes often had to be re-drilled, reducing productivity.Putting it bluntly, drifting androck bolting equipment wasstruggling to cope with thepower of the new rigs. It washigh time for fresh ideas.

Extensive development byAtlas Copco Secoroc came upwith the new Magnum SR range,which counters problems withbreakage and offers performanceto match that of the modern drillrig.

RR3/RT17 23/6/05 10:11 Page 45

The system was put through itspaces in mines, and in a variety of tunnelling projects. The resultswere unequivocal: service life and rig availability both enjoyed sharpincreases.

The tests showed that the MagnumSR systems increased service life by25-100% on the rods, gave better ser-vice life of the bits, and created veryhigh operator acceptance due to easy

uncoupling of the drillbits. This result-ed in higher drilling productivity,thanks to easy collaring, straighterholes and better equipment availabilityduring the drilling cycle.

Expanding Family

The Magnum SR thread system wasfirst introduced with the SR35, whichhas a comprehensive selection of

products for hole diameters of 43-64 mm.

The next addition to the family wasthe Magnum SR28 range. Tests haveshown that SR28 is perfect for therapid drilling of holes for rockbolts,but can also be used for small holedrifting. This new line replaces the tra-ditional R25 system in 33-35 mmdrilling.

Tests in rockbolting have shownconvincing increases in service life forboth SR28 rods and bits. As with allother Magnum SR products, the bitsare easy to uncouple, and as a resultthe drillstring is subjected to fewerdamaging shockwaves, facilitatingrapid changes and more holes drilled.All together, that means less downtimechanging bits and rods, and more timespent drilling.

Magnum SR35, together withMagnum SR28, are ultimately aimedat helping drillers advance their tunnelor drill rockbolt holes quicker thanever before. The most recent memberof the family is SR32, which is spe-cially designed for hole diameters of38-41 mm.

Dawn of a New Era

The trend in drifting and tunnelling is clear: the rounds are getting longer, and the rigs more powerful.Magnum SR was designed to with-stand the high pressures so typical of today’s underground drillingoperations.

Although Magnum SR is relativelynew to the market, the enthusiasmwith which it has been received, andthe performance that it delivers, havegiven an indication of the direction inwhich the product is heading. AtlasCopco Secoroc is genuinely confidentthat Magnum SR heralds the dawn ofa new era in drifting and tunnelling, aswell as for rockbolting.

The success of this innovativesystem is beyond dispute. Drillersusing it are not only drilling more and straighter holes than before,they’re also finding that Magnum SR lasts longer than any competingsolution.

by Anders Arvidsson

TALKING TECHNICALLY


Magnum SR bit ready to drill.

RR3/RT17 23/6/05 10:11 Page 46

Rock Engineering

In the context of definitions, it is oftenmore accurate to talk about rock engi-neering, as components from geologi-cal, civil, mechanical and miningengineering are combined to create theprocess presented in figure 1.

This global process can be verydetailed, or quite basic, dependingupon the magnitude of the miningoperation and the available resources.The fundamentals include: the defini-tion of the structural fabric of the rockmass including aspects such as joints,faults, shear zones; the evaluation ofthe mechanical parameters of theintact rock and structures; the identifi-cation and quantification of the failuremodes based on stress and structuralanalysis; the influence of the excava-tion mode; and the design of the rockreinforcement itself.

Differently formulated, it could besaid that stresses and rock structuresare the two most important factorsaffecting the stability of any excava-tion in natural strata material.Combination of various stressesregimes and fragmentation will dictatethe behaviour of the excavation (seefigure 2). Rock stresses intensity canvary from very low to very high, andintensity of fragmentation from mas-sive rock to sugar cube structure or

intensely schistose.Massive rock will drawmost of the intact rockstrength, but will alsoaccumulate load andcan fail violently underthe right conditions (seefigure 3). Very frac-tured rock will tend toyield to stresses, andoften deforms in aproblematic manner(figure 4). Obviously,excavation shape, sizeand orientation alsoaffect the response tothe acting forces atplay.

OptimizedExcavationAlthough rock mechan-ics is a relatively newscience that deals withthe mechanical behav-iour of rock material, it

TALKING TECHNICALLY


Rock Mechanics and RockReinforcement in MiningBehaviour of RockRock mechanics or geomechanicsis a term often used to include allthe steps that lead to define andcontrol the behaviour of rockaround excavations. From thegeological and mechanical defini-tions, through rock mass charac-terization, to the design ofreinforcement and calculation offactors of safety, rock mechanicsprovides the basis for the assess-ment of reinforcement needs.

Figure 1. (above) General process encompassed by the general definition of rock mechanics application tothe design of structures in rock. Figure 2. (below) Simplified description of rock mass conditions and rock failure (from Hoek E., P.K. Kaiserand W.F. Bawden. 1995. Support of Underground Excavations in Hard Rock. Balkema p215).

Massive rock subjected to low in situstress levels. Linear elastic responsewith little or no rock failure.

Massive rock subjected to high in situstress levels. Spalling, slabbing andcrushing initiates at high stressconcentration points on the boundaryand propagates into the surroundingrock mass.

Massive rock, with relatively few discontinuities, subjected to high insitu stress conditions. Failure occursas a result of sliding on discontinuitysurfaces and also by crushing andsplitting of rock blocks.

Massive rock, with relatively few discontinuities, subjected to low insitu stress conditions. Blocks orwedges released by intersecting discontinuities, fall or slide due togravity loading.

Heavily jointed rock subjected to low insitu stress conditions.The opening sur-face fails as a result of unravelling ofsmall interlocking blocks and wedges.Failure can propagate a long way intothe rock mass if it is not controlled.

Heavily jointed rock subjected to highin situ stress conditions.The rock masssurrounding the opening fails by slidingon discontinuities and crushing of rockpieces. Floor heave and sidewall closureare typical results of this type of failure.

Hea

vily

join

ted

blo

ckJo

inte

d r

ock

Mas

sive

ro

ck

Low stress levels High stress levels

Rock Mass Characterization

Structural failures and gravity

Shear analysis of critical structures

Evaluation of failure zones

Calculation of “factor of safety”

Determination of in-situ stress

Mechanical properties of rock masses

Evaluation of zones of high stresses

Calculation of reinforcement needsCalculation of reinforcement needs

Influence of blast and dynamic eventsInfluence of blasting

Reinforcement designReinforcement design

Failure caused by overstressing

Rock Mass classification and identification of failure modes

RR3/RT18 23/6/05 10:12 Page 47

is now regularly used to optimize theperformance of mining excavations inrock. Using rock mechanics leads to abetter understanding of the behaviourof the rock masses, which in turn leadsto a more effective and safer opera-tion. Stress analysis is also more com-monly performed on site, and resultsare easier to analyze thanks to the useof powerful desktop computers.

The design process should also berepeated at later stages of the miningoperation, as field conditions willalmost always change for the worse.It is critical that the correct assess-ment of failure mode is made, as thisunderstanding will lead to properreinforcement instead of using a longand arduous trial and error methodol-ogy.

As an example, when hard andmassive rock fails, producing smallfragments like those seen on figure5, it is often a sign that the rock isoverstressed and is rupturing in abrittle and uncontrolled way. Thiscould be the precursor of seismicevents and dynamic failure, whichmost rock reinforcement would beunable to control. It is also a factthat, as long as well-recognizedbrands of rock reinforcement areused, the support devices rarely failas a result of poor material quality,but rather as a result of inadequateapplications.

Numerical Modelling

Long term excavation planning canbenefit from detailed analysis likenumerical modelling. Stress regimescan be predicted and miningsequences optimized to keep the stresslevel at a comfortable level: not toohigh to create seismic events, and notto low to create major structural insta-bilities. For day-to-day operation,numerical analysis will give resultsthat must be confirmed by field obser-vation, but can be used to plan withthe right kind of conditions in mind.

This applies especially for the rockreinforcement and support aspects.

Some rock reinforcement and sup-port that can be perfect for static con-ditions may become quite inadequatewhen confronting seismic events orhigh stresses and deformations. It isthen important to be able to predictfuture conditions, and use rock rein-forcement that will still be adequatewhen conditions change, or will warnwhen in-situ conditions are close toexceeding the rating of the device.

Rock Reinforcement

Rock reinforcement devices and sur-face support are used to control therock masses within a certain range,allowing safe and economical accessto the excavated areas.

Historically, before the 1900s, typi-cal roof support in mines was timberposts and beam. Then, as early as1905, roof bolts were reportedly usedin coal mine roofs in the UnitedStates. In late 1920, systematic rein-forcement of mine roofs was intro-duced to allow the use of mechanicalfull-revolving loading shovels, by pro-viding room to manoeuvre free of con-ventional timber posts. Inclusion ofchannel irons, fastened by rock boltsto support large area of roof led to theprinciple of “suspension roof sup-ports”. The need for early support tosecure the lower roof layer to avoid

TALKING TECHNICALLY


Figure 3. Rubble created from a dynamic failure ofa mine roof.

Figure 4. Ground conditions leading to yieldingwalls and roof.

RR3/RT18 23/6/05 10:12 Page 48

loosening the upper layers, as well asthe creation of roof beam action, laidthe foundations of modern rock rein-forcement principles.

Around 1945, expansion shellanchors appeared in England, Hollandand US, and by 1949 rock bolts beganreplacing timber supports in USmines at a rapid rate. By end of 1952,over 2 million rock bolts per monthwere being installed. In Canada, sys-tematic bolting of roof in coal minesbegan in 1950. By the end of the1950s rock bolts were in use every-where, thanks to the systematic use ofmodern carbide tipped steels for fasthole drilling.

Rapid installation, compared totimber sets, was also compatible withmechanized mining methods. Between1952 and 1962 the introduction ofgrouted slot and wedge bolts, fullygrouted untensioned deformed bars, aswell as the hollow core groutableexpansion shell rock bolt, provided astrong argument in favour of perma-nent reinforcement with rock bolting.

During the 1960s, experiments weremade with epoxy and polyester resins asbonding media. By 1972, prepackagedpolyester resin systems were developed,tested and marketed. Immediatelyactive, full-length reinforcement of rockmasses became possible.

Quality of installation remained anissue, and lengths of bars, as well asresin quality and setting times, createddifficulties in installing the reinforce-ment system.

Modern Rock Bolts

By 1979, J.J. Scott introduced thesplitset rock bolt, and in 1980 Swellexbolts were introduced by Atlas Copco.These two products started the use offriction anchored rock bolts in under-ground excavation.

During the 1980s, the cone bolt, ayielding rock bolt better adapted torock burst events, was introduced inthe South African mines, and its appli-cation in other continents is still underdevelopment.

Around the same time, recognizingthe need for support in movingground, Atlas Copco introduced theYielding Swellex. In 1997, Atlas

Copco introduced the EXL Swellex,an all around high performance yield-ing friction rock bolt.

In 2003, Atlas Copco and MAIjoined their efforts and introduced theSwellex Pm Line and the mechanizedinstallation of SDA anchors. Today,Self Drilling Anchors that were firstdeveloped for ground engineeringapplications are slowly gaining groundas an alternative in extremely poorground conditions.

For long reaching reinforcement,cable bolts, coupled rebars and,more recently, connectable frictionbolts (Swellex Connectable) andSelf Drilling Anchors, provide a

large range of operational possibili-ties. Surface retaining supports likeshotcrete and reinforcing mem-branes are now adding anotherdimension to the reinforcement ofunderground excavations, and theiruse in combination with rock boltsprovides a counter-effect to stresses,water and time.

TALKING TECHNICALLY


Figure 5. Slabs created by the violent failure of amine roof during a small rock burst.

Figure 6. Estimated support categories based onthe tunnelling quality index Q (after Grimstad andBarton, 1993).

0.001 0.004 0.01 0.04 1 0.4 10 4 10 40 100 400 1000

REINFORCEMENT CATEGORIES1) Unsupported2) Spot bolting3) Systematic bolting4) Systematic bolting with 40-100 mm unreiforced shotcrete5) Fibre reinforced shotcrete, 50 - 90 mm, and bolting

6) Fibre reinforced shotcrete, 90 - 120 mm, and bolting7) Fibre reinforced shotcrete, 120 - 150 mm, and bolting8) Fibre reinforced shotcrete, >150 mm, with reinforced

ribs of shotcrete and bolting9) Cast of concrete lining

RQD Jr JwRock mass quality Q = x xJn Ja SRF

20

10

7

5

3

24

1.5

100

50

20

10

5

2

11

Exceptionallypoor

Extremelypoor

Verypoor

Verygood

Ext.good

Exc.good

Poor Fair Good

Spa

n or

hei

ght i

n m

ES

R

1.5 m

2.0 m

3.0 m

4.0 m(9) (8) (7) (6) (5) (4) (3) (2)

Bolt spacing in unshotcreted area

Bolt spacing in shotcreted area

1.3 m

1.0 m

1.0 m

150 mm

120 m

m90

mm

50 m

m

40 m

m

250 mm

1.2 m1.3 m

1.5 m 1.7 m2.1 m

2.3 m 2.5 m

RR3/RT18 23/6/05 10:12 Page 49

Adaptable Design

Rock reinforcement and rock mechan-ics applications are inter-related as thedesign of an excavation and its rein-forcement is an implicit process inwhich most parameters are interde-pendent. The design of excavationalso gets new “blood” with advancesin technologies. Better long holedrilling equipment provides straighterboreholes that allow larger stopeswith less development and betterblasting control, and improvements indilution and stability go hand in hand.

However, recognizing that groundconditions are going to change bringsthe need for easily adaptable designmethods of rock reinforcement. Inthis case, empirical methods can helprapid and sound decisions.

Figure 6 presents a rock rein-forcement design method based onthe tunnelling index Q. Fast andreliable ground control practices canmake the difference between a prof-itable extraction and a marginal one.

Conclusion

Rock mechanics in mining hasevolved tremendously over the last 15years with the availability of numeri-cal models that run on desktop com-puters, and the very active transfer ofknowledge and technology betweenresearch and mining operations. Infact, the practical application of rockmechanics in everyday mining is oftenconsidered a normal part of the extrac-tion process.

Rock mass classifications are usedsystematically in most mining opera-tions in North America, and openingsizes and shapes are carefullydesigned and planned to fit both theequipment requirements and the sta-bility limits.

It is true that mining operations areoften working at the limits of stabilityof excavations, but then the profitabil-ity of mining demands that knowledgeand applications are at the forefrontallowing the best overall performance .By developing local expertise and

sharing it through conferences andpublications, rock mechanics peopleare always pushing the limits of per-formance of excavations.

In order to get the full benefit ofrock mechanics application and rockreinforcement systems, the two mustbe linked and interconnected in a wayto provide feedback information anddata for each other.

During the past two decades, theimpact of accidents and damages hasbeen better understood. It has beenrecognized that the safer the environ-ment, the better the productivity andworking relations. Social costs arenow considered as valuable, andminimized. An objective of miningoperations all over the world is toeliminate working injuries. As rockfall incidents are often fatal, theyshould be avoided by using integrat-ed bolting systems to provide opti-mum reinforcement and supportsolutions.

by Francois Charette

TALKING TECHNICALLY


RR3/RT18 23/6/05 10:12 Page 50

Testing Configuration

Figure 1 shows the testing apparatusused to simulate the action of seismicevents on Swellex rock bolts. Allimpact tests were performed on 2.1 m-long Swellex Mn12 bolts. The staticweight of moving part was one metrictonne, or 1000 kg. In field failure, theSwellex bolts are usually broken at adistance varying from 10 cm to 50 cmfrom the head bushing. Failure of thebushing weld almost never occurs inthe field. To try to reproduce the fail-ure pattern observed in the field, theSwellex bolts were inflated in twosteel tubes, with the top tube generat-ing the anchorage. The second (seeFigure 1) shorter, impact tube alsogenerates some friction above thebushing and plate assembly, whichdampens the impact. The rationale isthat, since no bolts are breaking at thebushing weld in field events, it mustbe that the bulking occurs at such a

distance from the head as to mobilizeload from the anchorage and retainingforce generated by the bushing-plateensemble.

The friction inside the steel tubewas not sufficient to create failure ofthe bolt profile, and this highlightedthe need to better simulate steel/rockanchorage capacity. However, thisreduced friction demonstrated interest-ing behaviour that has led to a betterunderstanding of anchorage require-ments in dynamic loading.

Testing Procedures

The basic test procedure was: 1)turning on the electro-magnet andlifting the weight at the appropriateheight above the impact position onthe bolt; 2) initiating the dataloggingsystem (when used) to measureimpact load; 3) turning of the elec-tro-magnet to release the movingweight; 4) if no failure, or completesliding of bolt inside tube, the weightis hooked up again and lifted up forthe next drop. The load data was

TALKING TECHNICALLY


Performance of Swellex Rockboltsin Dynamic Loading ConditionsAvoiding DynamicFailureDynamic failure of rock under-ground can generate high levelsof kinetic energy and expulsionof rock from the opening surface.Rock material reaches velocitiesof a few metres per second andin those conditions, the rock rein-forcement is more than oftendestroyed or at least mobilized inexcess of its working range,resulting in caving or closed-inexcavation contours. Rock rein-forcement used in those condi-tions must be able to sustain theenergy burst, as well as retainingthe rock adequately before andafter the event. In order to assessthe Swellex capability in dynamicfailure conditions, laboratorytesting programmes have beenundertaken to quantify the per-formance of Swellex rock bolts indynamic loading conditions.

a

b

Figure 1. Testing apparatus with a) originalconfiguration and b) modified configuration fordistributed impact, and c) completed test withmodified configuration.

c

RR3/RT19 18/8/05 14:00 Page 51

measured at time intervals of0.00005 seconds.

Impact Tests Analysis

Upon starting the test, the weight iselevated to a pre-determined heightabove the impact point. After beingreleased, the weight accelerates until itreaches the impact point. At this point,the impact load is measured. Underthe impact load, the bolt starts todeform, but almost simultaneously, italso starts to slide inside the steel tube.The sliding reduces the load on thebolt, so that it does not fail if it is notpinned or restrained. During sliding,frictional energy is dissipated accord-ing to the friction generated on thewall of the tube. As the weight slowsdown, the friction coefficient increasestoward its static value, and the bolt isfinally stopped. The momentum cre-ates harmonic oscillations in the bolt,which acts as a stiff spring, and theseare damped very rapidly. When thebolt is clamped or fixed so that itcannot start to slide at both ends, if thetransmitted load at the restricted loca-tion does not reach the ultimatestrength of the steel, the bolt onlydeforms elastically and plastically,

according to the load level. If the loadreaches, or exceeds, the ultimatestrength, then the bolt simply breaks.However, based on the test results,

maximum dynamic strength differsfrom maximum static strength.

A summary of impact testing is pre-sented in Figure 2, including animpact test where the recording equip-ment was successful in picking up allof the information. Table 1 presentstypical results from the laboratory test-ing programme.

Analysis Of EnergyAbsorption CapacityTable 2 summarizes testing results onvarious types of rock reinforcementfixtures. Static steel properties can beused to preliminary assess the theoreti-cal energy absorption capacity, but ithas been found that load and deforma-tion are different from static tests.Measurements show that the impactload exceeds the ultimate static tensilestrength by a factor of about 1.5, whilewhen shearing was observed (Figure 3),the impact load exceeded the ultimateshear strength, taken as 60% of tensilestrength, by a factor of about 1.4.From the tests performed during thespring of 2004, the bolts showed onlyminimum yielding for loads exceeding

TALKING TECHNICALLY


Table 1. Typical Impact Tests Results

Result Test 1 Test 2 Test 3 Test 4

Impact Load (T) 10.4 15.3 17.8 18.2

K(kJ) 9.1 8.6 6.1 9.1

Status of bolt Failed in Failed in Failed in Slidedshear shear and tension

tension

Table 2. Theoretical energy absorption capacity based on quasi-staticload -strain properties

Description Peak Load Displacement Energy (kN) (mm) Absorption

(kJ)19 mm resin-grouted rebar 100 – 170 10 – 30 1 – 416 mm cable bolt 160 -240 20 – 40 2 – 616 mm, 2 m long mech. Bolt 70 – 120 20 – 50 2 – 416 mm, 4 m debonded cable 160 – 240 30 – 50 4 – 816 mm grouted smooth bar 70 – 130 50 – 100 4 – 10Standard Swellex bolt 105 – 110 25 – 35 2 – 4Mn12 Swellex bolt 120 – 125 45 – 100 5.4 – 12.5Mn24 Swellex bolt 220 – 240 80 – 120 18 – 29Split Set bolt 50 – 100 80 – 200 5 – 1516 mm cone bolt 90 - 150 100 - 200 10 – 25

(Data from Kaiser, 1995)

Figure 2. Typical signature of impact test on Swellex bolts: a) Typical phases of an impact test; b) actualimpact test with sliding of bolt inside steel tube.

Load

Time

A

B

C

25

15

5

-5Load

(to

nnes

)

Swellex Sample A1

time (s)0.95 1.05 1.15 1.25 1.35 1.45 1.55

A: ImpactB: Sliding of bolt inside tube sectionC: Harmonic oscillation of weightafter sliding has stopped.

The typical measurements of thetests are:

Impact loadSliding LoadFinal load on load cell(should be equal to themoving mass, i.e. 1 tonne)Time of slidingTime to failure (when it occurs)

RR3/RT19 25/6/05 13:28 Page 52

more than 50% of their maximumstatic strength. In fact, in dynamictesting, Swellex bolts elongated only32 mm with a load of about 17 t on thetest to failure, absorbing about 5.3 kJof energy, which is similar to theenergy absorption capacity calculatedfrom static testing.

When the rockbolt was notrestrained, loading was not accompa-nied by failure. The energy that a rockbolt can accept is smaller when the boltis pinned inside the tube (Figure 4),stretches to failure at the first blow. Bycontrast, when the bolt is able to slideslightly in order to avoid critical defor-mation, the impact energy that can beaccommodated is quite a bit higher.

The mechanical properties of thebolts’ components can give instructiveinsights on the energy absorptioncapability of a given bolt type. Table 2gives some typical results from Kaiser(2, 3, 4) and from NorandaTechnology Center (5). These resultstake in consideration only the elastic-plastic behaviour of the shank/body ofthe bolts when submitted to a staticload: the dynamic capacity is inferredin considering that the same load-deformation relationship would existduring dynamic events.

In Table 3, results from dynamictesting are presented and, fromOrtlepp and Stacey (1), Swellexanchored in steel pipes could absorb4 – 5 kJ of energy when sufficientanchorage is provided, or when the

sliding is restrained. Profile deforma-tion during the tests ranged from 42 to55 mm when the bolts broke. Theimpact was localized on the head onlyso the higher strength of the profilecould not be mobilized.

Results from Kaiser et al. (3) aswell as from Ortlepp and Stacey (1),outline the fact that most reinforce-ment fixtures have limited capacitiesof absorbing energy when usingdeformation/yielding properties, andvalues range from 1 to 25 kJ ofenergy at most. However, when areinforcement fixture dissipates

energy through sliding, its energyabsorption capability is enhanced.Results from NTC’s tests on Swellex(2003) and Cone bolts (1998) showthat, on a single event, it is possibleto dissipate over 9 kJ with a Standardsize Mn12 Swellex, which might bemore with rougher tubes and longerbolts, and about 22 kJ with the Conebolt tested at NTC (Kaiser). Thesevalues exceed by far any strainenergy accumulation mechanism. It isimportant to understand that, indynamic loading, ultimate load anddeformation are not the same as in

TALKING TECHNICALLY


Bolt Type Source Single Event

Cone Bolt Kaiser Variable (NTC) from and al. withKaiser and Max: 22 kJal.

Swellex Ortlepp 4.1 – 5.1 kJand Stacey

Rebars Ortlepp 4.1 – 5.5 kJ andStacey

Swellex Atlas 9 kJMn12 Copco/2.1 m NTC

Table 3. Energy absorption capacity from dynamic testing

Figure 3. Failure of Swellex bolt in shear.

Figure 4. Failure of bolt at pin location.

RR3/RT19 18/8/05 14:01 Page 53

static loading, but the deformationalenergy absorption seems to be quitesimilar.

Tests results from NTC and AtlasCopco also demonstrated anotherimportant fact. This is that maximumenergy can be absorbed when the fric-tion properties are tightly matched tothe strength of the material. When thisright combination is reached, the bolthead will move just before theshank/bolt body enters the deformationphase. This allows maximum energyabsorption without failure of the unit,and provides a consistent energyabsorption capacity, coupled withstable static load bearing capacity,equivalent to the rated capacity of thebolt.

Conclusion

Dynamic testing at the laboratory hasshown that Swellex bolts can acceptand dissipate a reasonable amount ofenergy without failing, and still providean adequate load capacity, as long asthe anchorage length is adequately

coupled to the static anchorage capaci-ty. This operation was successful withsteel tubes instead of rock. The nextstep is to increase the friction againstthe bolt in order to simulate an anchor-age capacity of 130 to 180 k/m, andrepeat the same testing with Mn24bolts.

It is also very interesting to consid-er what kind of energy dissipationcould be achieved when using anMn24 instead of an Mn12 bolt. As thebolt itself is twice as strong, the maxi-mum load could be doubled, and,since the friction could be adjusted inorder to provide the right anchoragecapacity, the energy absorption couldcertainly be in the order of +18 kJ perevent.

The conclusions obtained fromthese laboratory tests is beingapplied to the Hybrid Swellex boltthat combines the controllable slid-ing ability of the Swellex with thestrength and reliability of MAIbars.


TALKING TECHNICALLY


References

1. Charette, F. Performance ofSwellex rock bolts under dynamicloading conditions, The SouthAfrican Institute of Mining andMetallurgy. Second InternationalSeminar on Deep and High StressMining, Johannesburg 2004.

2. Ortlepp, W.D., Stacey, T.R.Testing of tunnel support: Dynamicload testing of rock bolt elements toprovide data for safer supportdesign (GAP423), June 1998.

3. Kaiser, Canadian RockburstDesign Handbook, 1995.

4. Kaiser et al, Drift Support inburst-prone ground, CIM Bulletin,March 1996.

5. Kaiser, Support Against RockBurst – Short Course 1995–2003.

6. Falmagne, V. Etude de fais-abilité: tests d’impact sur Swellex.Centre Technologie Noranda, Mai2003.

RR3/RT19 25/6/05 13:28 Page 54

Advantages of Self DrillingAnchorsSince the slow cased borehole drillingmethods were superceded, the speedof installation has increased consider-ably, up to 20-30 soil nails/day usingMAI SDA, and the risk of re-drillingtime spent cleaning collapsed bore-holes has been eliminated.

The selection of the drilling equip-ment for MAI SDA installation is alsomore flexible, especially for workingin confined space.

MAI SDA rods are manufacturedwith a continuous ISO standard

thread, affording the flexibility toadjust the nail to the actual require-ments on site, without waste or delay,as construction proceeds.

Transportation and handling ofMAI SDA to and on site is safe andeconomical, because of the commonlyused rod length of 3 m or 4 m. Thesecan be extended using couplings toallow installation of soil nails up to 15m depth, depending on the geology.There is also the option to use simulta-neous drilling and grouting installationtechniques.

Method of Installation

Self Drilling Anchors are installedwith air driven or hydraulic rotarypercussion drilling equipment, usinga borehole flush medium suitable forthe specific ground conditions.

There are three types of boreholeflush: water flush for long boreholes indense to very dense sand, gravel forma-tion or rock conditions, for a bettertransportation of large cuttings and cool-ing of the drill bit; air flush for shortboreholes in soft soil such as chalk and

TALKING TECHNICALLY


Slope Stabilization with SelfDrilling AnchorsSoil Nailing forReinforcementSoil nailing is used to reinforce

and strengthen ground which has

questionable stability. Soil is gen-

erally a poor structural material

because it is weak in tension.

Steel, on the other hand, is strong

in tension. The fundamental con-

cept of soil nailing is to effectively

reinforce soil by installing closely

spaced grouted steel bars into a

slope or excavation, as construc-

tion proceeds from the top down.

A soil nail is therefore commonly

referred to as a “passive” anchor-

ing system, meaning that it is not

pre-tensioned, as is normal with

ground anchors.

Unstable slopes or excavations

consist mostly of unconsolidated

soils or deteriorated rock forma-

tions. To install conventional soil

nails, a cased borehole drilling

method is required to overcome

such difficult and unstable

ground conditions. An alternative

is the MAI Self Drilling Anchors

(MAI SDA), which is specially

designed for use in ground where

the boreholes tend to collapse

during the drilling process if

casings are not used.

Installation of SDA R38 N with ROC D7 at Carriere d’Arvel, Switzerland.

RR3/RT20 23/6/05 10:17 Page 55

clay, where water spillage is to be avoid-ed; and simultaneous drilling and grout-ing (SDG) for all lengths of boreholes inall unconsolidated soil conditions.

Using SDG, the grout stabilizes theborehole during installation, providing

a better grout cover along the nailshaft. The grout has good penetrationinto the surrounding soil, so higherexternal friction values are reached,and the installation is completed in asingle drilling operation, saving time.

By utilizing a sacrificial drillbit, theMAI SDA is drilled continuously for-ward without extraction, until the designdepth is reached. To reach a required naillength of 12-15 m, the 3 to 4 m standardrod lengths are easily coupled together.

When using the first two flushingmedia for the drilling operation, thesoil/steel interface has to be created bygrouting through the hollow stem ofthe anchor. The grout exits through theflush holes of the drillbit, and backfillsthe annulus around the nail that hasbeen cut by the larger diameter of thedrillbit.

For the third operation, the flushingmedium is already a grout mix, whichhas the ability to harden after theinstallation process is completed.

A typical application of SDA iscurrently being carried out by the opencast mine Carriere d’Arvel inSwitzerland. Here an Atlas CopcoROC D7 drillrig equipped with aCeminject (integrated rotary injection)adapter and a rod handling system isbeing used for SDA installation.

The ROC D7 feed reaches to aheight of 7 m, allowing installation oftwo rows of SDA from one position.

The rod handling system containsat least two sets of three 3.5 m-longR 38 N SDA rods, facilitating installa-tion of two complete 10 m-long SoilNails without having to manually feed

TALKING TECHNICALLY


Galvanized MAI-SDA R 25 and R32 anchorsinstalled into loose and collapsing ground usingsimultaneous drill and grout at the ShortlandsJunction, Bromley, Kent, UK.

Principle of the MAI Self Drilling Anchor.

ROC D7 offers excellent reach with a folding boom.

RR3/RT20 23/6/05 10:18 Page 56

extension rods at these extreme work-ing heights.

The newly developed integratedinjection adapter (Ceminject) can beused for either simultaneous drillingand grouting, or as in this case, firstdrilling to full depth with an air flushand then grouting the annulus of theborehole. The SDA installationbecomes a fast continuous mechanizedprocess with high grouting quality in asafe working environment.

Similar methods were used to stabi-lize the slope at Shortlands Junction,Bromley, Kent, UK, where loose andcollapsing ground was affecting opera-tion of the railway.

Installation Using ROCDrillrigsThe use of self drilling anchors for sta-bilization and reinforcement work insoft rock is common both in the under-ground world of mines and tunnelsand, for a wide variety of applicationson the surface.

On surface, it is generally poorquality ground and soil that threatenthe stability of installations or land-scapes. Embankments along roads andrailways, various types of foundationsand hills prone to landslide, and thesidewalls of cut-and-cover tunnellingare just a few examples.

Field tests have shown that theAtlas Copco ROC D-series of drillrigscan be used to install self-drillinganchors (SDAs), as well as for blast-hole drilling. Hence, contractors whoown one of these crawler rigs for quar-rying operations are perfectly-equipped to take on stabilization jobs.

A simple conversion kit enablesthis rig to be converted to an SDAinstallation unit, without losing theadvantages of the ROC D7 standard,high-tech features.

The rock drill is fitted with a kitconsisting of an Ceminject (integratedrotation injection) adapter, swivel andbrackets to replace the standard shankadapter. The SDA shank adapter is afemale shank having integrated couplingsleeve to ease uncoupling. Available forR32 and R38 anchors, it requires aflushing head with inner diameter of 53mm, normally used on surface crawlers,because of the size of the female frontpart of the shank adapter.

Ceminject is a SDA shank adaptercombined with a separate swivel pro-viding flushing media and grout. Theswivel is mounted on the rock drill witha bracket and has two separate inlets.The Shank Connector is a couplingsleeve locked to the shank adapter. Toprovide the locking function a specialmale T38 shank is required. This is analternative to SDA-shank, wheninstalling R51 or T76 anchors and whenalternation between bolting and blasthole drilling is required. A flushing headwith inner diameter of 53 mm is needed.

The Rod Handling System RHS 52is used for carrying bolts on surfacecrawlers. The system is equipped withSDA bushing halves in the grippingarms and the star wheels carrying therods.

BSH 110 is a hydraulic drill steelsupport providing gripping and guid-ing function. To drill SDA it isequipped with the rubber bushing andsteel bushing halves to match theanchor size.

The grout pump m400NT, availablefrom Atlas Copco MAI, is also recom-mended.

Two-man Operation

Only two people are needed – one tohandle the drilling, and one to handlethe pump. The SDAs, with their Rthreads and sacrificial bits, areinstalled and grouted in one operation.

These easy adjustments will enableROC D7 owners to get the best, andthe most, out of their equipment. Forsome, it may open up whole new mar-kets that they have previously noteven considered.

The beauty of being able to adaptthe ROC D7 for such applications isthat the contractor can make full useof the rig’s powerful and flexiblehydraulic system. The folding boom,for example, can be positioned up to aheight of 7 m beside a slope, or verylow for horizontal toe-hole drilling. Itcan also be positioned at extremeangles, enabling SDAs to be used invery inaccessible places.

Connecting Grout Pumpand Ceminject adapterMost of the time there is a need toalternate between flushing with waterand grout. In surface SDA installation,it may be inconvenient to grout duringdrilling, as this may contaminate thefeed with the grout, or minimizespillage during collaring. The alterna-tive is to flush with water whendrilling-in the anchor, and then grout itthrough the Ceminject. This would bethe final step in the installationsequence, prior to uncoupling the lastrod from the rock drill. To alternatebetween water and grout, connect thegrout pump and water hose to a y-cou-pling equipped with two valves, sothat water or grout may be selected.The hose from the y-coupling is thenconnected to the Ceminject, eitherdirect or by letting it run on the feedthrough the hose tree and over thehose drum. This type of y-couplingrequires manual switching betweenwater and grout.

When installing SDAs using a sur-face drillrig, some contractors have

TALKING TECHNICALLY


Atlas Copco ROC D7installing MAI SDAfor soil reinforcementusing MAIm400NTgrout pump.

RR3/RT20 23/6/05 10:18 Page 57

chosen to drill and grout simultaneously,using only grout as the flushingmedium. This has the advantage that,once the anchor is completely drilledinto the ground, it is fully groutedand ready to be attached to the faceplate. This makes the connectionbetween the grout pump and theCeminject straightforward, needing

only a single hose. It is possible toreplace the hose for air flushing bythe grout hose by attaching it to thehose tree and letting it run over thehose drum to the rock drill.

To simplify the system further, and toreduce number of people needed to dothe installation, two hoses can be con-nected to the Ceminject, one to the grout

pump and the other to the water flushingsystem on the rig. The water supplyhose should be equipped with a non-return valve at the connection to theCeminject, in order to prevent groutfrom entering the water system. Thetwo hoses can be put on the feed overthe hose drum.

This system makes it easier to con-trol both water and grout flushing,with the water controlled by a valveon the rig, and grout flow by startingand stopping the pump. The groutpump can be controlled remotely bythe rig operator, or by the pump oper-ator on demand from the rig.

SDA Installation Cycle

The optimal SDA installation cyclecomprises the following steps:

1. Drill first SDA rod, either withsimultaneous drilling and grouting orwith conventional air or water flush,guiding with the Drill Steel Support(DSS) in open position. When the rodhas fully penetrated into the soil/rock,stop the flush and loosen the rod endconnection to the drifter by clampingthe DSS and unscrewing the femaleshank adapter. Uncouple beforeretracting the rock drill.

2. Extend with next rod using the rodhandling system, open DSS and com-mence flushing, then resume drilling.

4. Repeat rod-adding sequence untilfinal design length of the anchor hasbeen drilled.

5. If simultaneous drilling andgrouting modus has been used, thenthe installation cycle is now completeand the feed can move to the nextanchor position.

6. In air- or water-flush modus,switch over to grouting mode and,while maintaining a slow rotation ofthe anchor, commence grouting untilthe hole is full. The in-situ rotationmixing process of the grout guaranteesa homogeneous filling of the annulus,improving corrosion protection andexternal friction values of therock–grout interface.

7. The installation cycle is complet-ed and the feed can move to the nextanchor position.

by Mark Bernthaler

TALKING TECHNICALLY


Standard rod handling magazine with SDAs and couplings.

The special bushing halves prepared for firm gripping of the SDAs.

COP 1832 rock drill with Ceminject adapter.

RR3/RT20 23/6/05 10:18 Page 58

Introduction

Currently the assessment of potentialfor excessive overbreak and disconti-nuity controlled block falls or slidesheavily relies on experience.Measurement of discontinuity patternand orientations is done manually, ifat all. The evaluation of the incom-plete and inaccurate data with respectto block fall hazard is slow, and usual-ly does not allow for the determina-tion of appropriate rock support intime.

In order to master these shortcom-ings with respect to efficiency andaccuracy, a 3D imaging system hasbeen developed consisting of an imag-ing device and 3D evaluation softwarecomponents. Named theJointMetriX3D® system, it unites sev-eral features:

• Data (image) recording at the face• 3D image generation and assessment• Metric and accurate measurement

of discontinuity orientations, dis-tances, persistence, and other geo-metrical properties

• Link to other applications, such asCAD

A 3D image combines a largenumber of three-dimensional surfacemeasurements with a high-resolutioncolour image, thus easing visualinspection of the rock mass.

Imaging at the Tunnel Site

The major goal is to record the actualrock mass conditions comprehensivelyby producing images that allow repro-ducible assessments. The stereo-pho-togrammetric principle ofJointMetriX3D® requires two imagesof the same area captured from differ-ent positions in order to obtain 3Dinformation. Currently, two options forimaging are available. The first oneuses conventional calibrated singlelens reflex (SLR) cameras, while theother uses a panoramic line scanner.

SLR Camera

A conventional SLR camera with aminimum 6 MPix sensor is used to

take two free positioned images. Inorder to allow for measurements, thecamera is calibrated. Scale and localorientation is introduced by locating avertically levelled bar somewherewithin the region of the images.

The whole data acquisition processrequires only about one minute.Processing the images leads to 6 MPix3D images with several hundred thou-sand 3D measurements.

Panoramic Line Scanner

For very high-resolution images, thepanoramic line scanner should beapplied. This scanner is capable ofproducing images of more than 100Mpix, recording very fine details.During scanning, the device headrotates, recording the face column bycolumn. A major advantage of thepanoramic principle is that existingreflective targets in the tunnel can beused to establish a reference of theimage to the tunnel. Data acquisition

TALKING TECHNICALLY


3D Images for the Design ofRock SupportReducing Rock FallHazards in TunnelsRock blocks falling from the roofor sliding into the tunnel can be ahazard for the miners and equip-ment, besides generating addi-tional costs. Efficientidentification of potentiallyunstable blocks and instantdesign of appropriate rock rein-forcement thus contributes tosafer and more economicaltunnel construction.

A recently developed imagingsystem and evaluation softwareassists in identifying unstableblocks and design of rock sup-port.

Evaluated 3D image generated with JointMetriX3D®. Joints are represented by traces and areas. Thearrows indicate the orientation of an area by its normal vector while the spherical triangles indicate theorientation of the plane fitted through the trace. The absolute position and orientation of the joints isdirectly determined.

RR3/RT22 23/6/05 10:23 Page 59

TALKING TECHNICALLY


on site typically takes in the region often minutes, leading to 3D imageswhich are referenced to the tunnelcoordinates.

3D Image Generation andMeasurementsFrom a stereoscopic image pair a 3Dimage is reconstructed by purpose-built software. This can be carried outby personnel on-site or off-site, usingsecure Internet connections.

Once a 3D image is ready, assess-ments and measurements are takenfrom it using the 3D software JMXAnalyst. This software allows theinspection of 3D images thoroughly,giving a realistic impression of theactual conditions.

Measurements are taken directly onthe 3D image using the software, suchas:• Joint locations, orientations, spac-

ing, persistence, etc.• Lithological boundaries• Areas• Volume of overbreak

JMX Analyst contains a tool to plotjoint data in stereographic projectionand the variation of orientations ofjoint sets (cone of confidence, spheri-cal aperture, etc).

All measurements are metric andreferenced either to a relative or thetunnel coordinate system, and can beexported directly into standard file for-mats.

A free copy of JMX Analyst isavailable for download at www.joint-metrix.com/.

Prediction of Block FailureModes and Support DesignThe measurements derived from 3Dimages are used to establish a consis-tent and accurate ground model. Usingthe acquired information on the rockmass structure, potentially unstableblocks are identified with respect totheir location, volume, and weight.

Once the failure mode and theproperties of the blocks are identified,the quantity, location and length ofrequired bolts to stabilize the blocks isdetermined.

Further processing of the existingdata can be used to extrapolate therock mass structure in a representa-tive volume around the tunnel,allowing an assessment of the condi-tions ahead of the face. Thisenhances the quality of short-termprediction, thus reducing any sur-prises during excavation.

An imaging system, such asJointMetriX3D® can be installed on adrilling jumbo, allowing for an instantimaging during work. Recorded dataare transferred to the office for evalua-tion, and the necessary information forthe rock reinforcement transferredback to the drilling equipment withinminutes.

by Wulf Schubert, Markus Pötschand Andreas Gaich

Rock block support by bolting during tunnel excavation .Prediction and final design is based on the rock mass structure derived from JointMetriX3D® measurements.

3D imaging with SLR camera.

RR3/RT22 23/6/05 10:23 Page 60

Competence Centre

The Atlas Copco Competence Centreteam was looking for a type of rock boltoffering the following features: immedi-ate and efficient support; immediateanchorage in any type of rock; adapt-able to any hole lengths; fast and trou-ble-free installation; longevity whenrequired; pre-tensioning capacity whenrequested; and the possibility to controlthe anchorage capacity and behaviourof the rock support to maintain the boltintegrity in case of seismicity.

Shortly after Atlas Copco acquiredthe reputable MAI SDA system, it

became apparent that the solution wasto combine the two.

Equipped with a Swellex end, thenew rock bolt offers immediateanchorage. As only a short segment ofSwellex is required, the product maybe installed in long holes by simplyadding new MAI SDA segments.Good anchorage capacity in any typeof rock is another advantage of using aSwellex segment at the end of the bolt.Furthermore, as a plate and nut arefastened on the MAI rod side, real pre-tensioning is possible.

A special coupling has been devel-oped to connect the MAI rods and theSwellex segment for the purpose ofgrouting, offering longevity whileadding stiffness in shearing.

By limiting the length of the Swellexsegment, the anchorage strength can becontrolled. Sliding behaviour at hightensile load consumes energy withoutcompromising the integrity of the bolt,with the insurance of a perfect, low-costinstallation every time.

Pre-tensioning andGroutingThe vast majority of grouted rebarsand cable bolts are not pre-tensioned,mainly because this process is cum-bersome and time consuming. Theneed for pre-tensioning is higher ifground movement is likely to occurduring the cement curing period.

As pre-tensioning creates an activesupport, larger stress can be absorbedwithout rock failure.

The Swellex segment and thegrouting device are inserted first, fol-lowed by as many MAI SDA rods asneeded to reach the required length.The Swellex segment can then beinflated through the MAI SDAanchors. A plate and nut are installedafter inflation to provide immediatesupport and real pre-tensioning.Grouting can then be carried outimmediately, or later, once equilibriumhas been reached with no furthermovement of the rock mass expected.

The grout then achieves higherstrength and resistance.

Seismicity

Most of the present generation of rockbolts, such as cone bolts and durabar,that address the seismicity problem

TALKING TECHNICALLY


Introducing Swellex HybridNew VersatileRock SupportBy combining the benefits ofSwellex bolts with those of theMAI Self Drilling Anchors (SDA)system, Atlas Copco has devel-oped a new versatile type of rocksupport that can be pre-ten-sioned, grouted or use as a rockreinforcement system for seis-micity.

The new Swellex Hybrid pro-vides immediate support, longlife expectancy and the level ofsafety and productivity character-izing Atlas Copco RockReinforcement products. By cou-pling MAI SDA bolt sections, thesystem can be installed in verytight locations to virtually anyhole length.

1

2

3

4

5

6

7

8

9

Components

1- Retainer

2- Swellex Connectable(blind segment)*

3- Grouting valve*

4- MAI Anchor Rod R32(hollow bar)

5- MAI Anchor Coupling

6- MAI Anchor Rod R32

Installation sequence of Swellex Hybrid for pre-tensioning and grouting.

Hybrid bolt for long anchorage in rock.

* Notes - The Grouting valve(3) is included with thespecial version of Swellex Connectable(2)when Hybrid bolt is to be grouted. - A standard Swellex Connectable blind seg-ment (2) is used when the hybrid is to beused for energy absorbancy.

8- Nut9- MAI Anchor Adaptorsfor Swellex inflation andgrouting

7- Face Plate

RR3/RT24 19/7/05 8:48 Page 61

TALKING TECHNICALLY


use the same principle of having a partof the system that can disengage andabsorb energy through friction or defor-mation. The efficiency of these systemsdepends on the quality of the installa-tion, which varies significantly with thequality of grout and de-bonding agent,rock mass condition, and experienceand training. Often, because of poorquality of installation, these systemshave not achieved the expected successand efficiency underground.

The advantage with the Hybridsystem is that, once the anchoragecapacity (kN/m) is deduced from on-site pull test of the short Swellex seg-ment, it is easy to calculate the lengthof the Swellex required to reach themaximum sliding strength that wouldnot damage the bolt under dynamicconditions, and the free sliding lengthneeded to dissipate the energy. Theinstallation is easy and, above all,always perfect, as it is controlled bythe Swellex pump. The installedsystem can also be tested at any timeto make sure it is working accordingto calculation.

Site Testing

The Hybrid bolt is now being tested atWASM facility in Australia to deter-mine the optimal anchorage for maxi-mal energy absorbancy of the systemunder dynamic loading conditions. Boththe Hybrid bolt and its system of con-trolled energy absorbancy are patented.

If, for example, a 1 m SwellexPm24C offering a 150 kN anchorageis proven to slide (yielding strength =200 kN) under dynamic conditionswithout damaging the bolt, a sliding of0.15 m would consume as much as22.5 kJ of energy.

Once sliding behaviour is tested andthe system proven, a sliding pull test(on a short bolt segment inflated) per-formed on site will confirm the anchor-age capacity. The length of the Swellexwill then be chosen to match the maxi-mum sliding strength, and sliding dis-tance calculated according to the energyto be dissipated. This system offers thefacility to be tested at any time.

Recent studies have shown that thequality of surface support is of para-mount importance for ensuring the

efficiency of rock reinforcement forseismicity, in order to make the systemabsorb the energy and preserve therock mass between each bolt.

Life Expectancy

When it comes to protecting theinvestment, for long life expectancySwellex Hybrid offers solutions tomatch the threat.

When used for pre-tensioning andgrouting:

Atlas Copco has developed a spe-cial grouting device that is coupledbetween the Swellex segment andMAI rods. This allows the SwellexHybrid to be inflated, pre-tensionedwhen required, and then groutedthrough the MAI SDA rods. Thegrout then protects the Hybrid bolt,preserving the MAI rods from contactwith the environment. For full protec-tion from a corrosive environment, orfor long life expectancy, MAI rodscan be supplied galvanized, andSwellex in Plasticoated or coated ver-sions. The grout will then offer thefirst protection layer, followed by thezinc layer, or the plasticoating on theSwellex. As the MAI bolts are groutedfrom inside out, there is no access forcorrosive elements.

When used for seismicity, Swellexplasticoated and galvanized MAI SDAanchors are recommended for corrosionprotection. A plug can be used to protectthe inside of the Swellex in the long term.

Installation Sequence

For pre-tensioning and grouting:1-Drill the hole to the required

length using 48 to 51 mm bit.2-Insert Swellex (the length can be

determined from pull test – shouldbe sufficiently long to generate pullout resistance equal or higher to itsyielding strength into the hole).

3-Thread the SDA rod all the way intothe grouting valve on the Swellex.Extend with additional SDA rodsand special Hybrid couplings (goodfor 300 bar) to match the hole depth.

4- Install plate and nut5-Attach inflation coupling to the

last SDA rod.6-Inflate Swellex through the SDA

rods using a standard Swellex pumphaving 300 bars in water pressure.

7-Open the grout valve (in the Groutingdevice) by rotating the MAI rods bya 1/2 turn anti-clockwise.

8-Detach the inflation coupling.9-Pre-tension the bolt.10-Grout (MAI 400 NT Grout Pump

is recommended).

For seismicity:1-Drill the hole to the required length

using 48 to 51mm bit.2-Insert Swellex (the length can be

determined from pull test – shouldbe sufficiently short to generate pullout resistance lower to its yieldingstrength into the hole).

3-Thread the SDA rod to the Swellex.4-Install plate and nut.5-Attach inflation coupling to the last

SDA rod6-Inflate Swellex through the SDA

rod using a standard Swellex pumphaving 300 bars in water pressure.

7-Detach the inflation coupling.8-Pre-tension the bolt.

By combining the merits of theSwellex and MAI SDA systems, AtlasCopco has invented a completely newapproach to rock bolting.

by Mario Bureau

Installation sequence of the Atlas Copco SwellexHybrid.

RR3/RT24 19/7/05 8:48 Page 62

Forward Stabilization UsingSwellexIn single-face development, high-speedrockbolting obviously cuts the time tocompletion. But in multiple face develop-ment or ore extraction, the objective is toutilize manpower and equipment efficiently,as well as to advance the faces on

schedule. This means that operations mustbe synchronized so that one does not fallbehind, holding up the others and wastingtime and money.

The development of Atlas Copco’sRocket Boomer and Boltec rigs isconstantly reducing drilling time, makingSwellex the perfect partner to providereinforcement quickly, so that the nextoperation can start without delay.

Drilling ahead of the tunnel face toinstall bolts or grout as pre-reinforcement,is a common way of improving the rockquality before excavation takes place.Instead of relying on supporting the groundfollowing excavation, pre-reinforcementincreases rock strength prior to excavation.

There are several benefits to this. First,a pre-reinforced rock mass will be lessdamaged, both by blasting and by theelastic and non-elastic stress redistributionof the excavation process. Second, the rock mass is never without support, even at the split second following blasting of the round. Third, the support can be more active when installed early, ratherthan passive when installed later. Fourth,pre-reinforced ground will not deteriorateor collapse as rapidly as a totally un-supported excavation, allowing a safeworking period for installation of regularsupport.

The Bieniawski diagram shows the rela-tionship between the unsupported span andstand-up time of an excavation with refer-ence to its rock mass quality. Empiricalobservations have shown that, for a given

MINING WORLDWIDE


Bieniawski diagram showing stand-uptimes for different spans and rockclasses.

Swellex in MiningSafe and SpeedySupportRock support is often a bottleneck inthe business of underground mining,and an obvious solution is fasterrockbolting. The cost is negligiblewhen compared to the higher profitsthat can be made by keeping equip-ment fully and economically employedto increase production.

The mining industry is increasinglyrecognizing that Atlas Copco Swellexrockbolts, which are quickly andsafely installed to give immediatesupport, are speeding up operationsand boosting revenues. Over the pasttwo decades, the Swellex rockboltingsystem has become world famous asthe simplest, fastest and most reliableground reinforcement technologyavailable.

The Swellex bolt is a folded steeltube, which is inserted into a pre-drilled hole in the rock. Water isblasted into the tube at high pres-sure, blowing out the fold andexpanding the tube into the exactshape of the hole, adapting to everyirregularity.

Bolt installation takes less than 30seconds, and provides full and imme-diate support along the entire holelength, in ground conditions rangingfrom the hardest rock to clay andeven non-cohesive material.

The system speeds up rock rein-forcement considerably and, over theyears, has built up an enviable repu-tation for saving time and money, aswell as providing a safer under-ground environment for miners andtunnellers alike.

In the tunnelling business, Swellexbolts are already accepted as the keyto better operational efficiency. Nowthey are ensuring higher advancerates, productivity and quicker accessto orebodies in mines as well.

RR3/RC1.qxd 23/6/05 10:46 Page 63

excavation size, a linear reduction in RockMass Rating (Bieniawski, 1974) will leadto a logarithmic reduction in unsupportedstand-up time. Hence, a linear increase inexcavation span results in a logarithmicincrease in instability potential. For largespan drifts, the time period available toinstall roof support is significantly lowerthan for small drifts. In the case of a 4.3 m-span tunnel driven through poor to verypoor quality rock, it may be logisticallyimpossible to support the roof before itcollapses. Obviously, the operational andsafety implications of such cases areimportant.

Field observations show that cable boltsinstalled in stopes before the first blocksare blasted are more effective than cablebolts installed after the slot or cut has beenexcavated. For cable bolts installed prior tostope exploitation, the grout curing periodis generally respected. This is not alwaysthe case for cable bolts installed during

stope exploitation, when production con-cerns may override ground support designconcerns. The cohesive effect of the cableis greater when added to undisturbedground than when added to weakened anddisturbed ground.

In tunnelling, the umbrella groutingmethod of pre-reinforcement is frequentlyused. This method pre-supports theplanned roof area with steel rods. Largeholes are drilled in the future roof peri-meter, and grouted at high pressure withhigh strength, fine grained cement grout.Through each cemented hole, a smallerhole is then drilled, in which a high-strength reinforcement bar is grouted.Although highly effective for shallow tun-nels driven in very adverse ground condi-tions, it is easy to see that such awork-intensive operation would be deemedneither practical nor economic for miningapplications, although the underlying con-cept could definitely be useful.

MINING WORLDWIDE


Mine Doyon ExperienceA variation of the umbrella method wasattempted at Mine Doyon, located nearRouyn-Noranda, in northwestern Quebec.The Mine Doyon property is one of the mostimportant gold-bearing orebodies in produc-tion in Canada. At least four major ore zonesare found on the Doyon property. Economicmineralization is found on a corridor thatextends at least 2 km E-W, and from surfacereaches a depth of over 1,000 m.

The No.1 Ore Zone is defined by amajor quartz and sulphide vein system,oriented E-W. The orebody is also orientedE-W, dips steeply south, and has an aver-age width of 8 m at depth. It is surroundedby sericitic schist corresponding to thesub-unit 4b of the Blake River Group(Savoie et al, 1991). Mining method islong hole stoping, with cemented rock fill.Mill production is around 3,500 t/day.

Several tectonic events have beenidentified, among them a N-S compression

followed by a N-S extension; an inverseshearing caused by a NW-SE compression;and a polyphased fracturing caused by anas-yet undetermined stress gradient.

The footwall of the No. 1 Zone is locatedin very poor quality sericitic schist, withRock Mass Rating values between 0 and30. This alteration zone runs for about 100m up to the ore body, which is located invery weak chloritic schists. Stope develop-ment in this ore zone was delayed due torepetitive caving in access drifts.

The rock mechanics engineer at MineDoyon designed a pre-reinforcementmethod using cable bolts installed over thefuture roof of the access drifts. An array ofnine 50 ft cable bolts was used to pre-support the roof during drift development.The method was successful from a rockmechanics point of view, allowing three tofour rounds to be taken before installingheavy support consisting of vertical cablebolts and shotcrete. Primary support couldbe installed during the normal cycle with-out safety problems.

Although stability was achieved, pro-ductivity was compromised, since thebolter was tied up in stope preparation andrehabilitation work. Also, since severallevels were being developed concurrently,travel time for the equipment and cablegrouting crew was significant. A bettersolution was needed.

Project: Underground gold mine pre-reinforcement.Location: Mine Doyon, Rouyn-Noranda, Quebec.Mining method: Longhole stoping with cemented rock fill.Rock: Quartz and sulphide veins surrounded by seritic schist.Rock reinforcement required: Protective umbrella in accessdrift. Rockbolt selected: Super Swellex.

RR3/RC1.qxd 23/6/05 10:46 Page 64

Requirements were: easy integration inthe normal development cycle; installationbefore the next drift advance; effectivesupport; and reasonable cost.

In order to increase productivity andregain some flexibility, it was decided totry pre-reinforcement using Super Swellexbolts instead of cables, and to slightlyreduce drifting length to about 3 m. Five tosix Super Swellex, parallel and spaced 60 to 75 cm apart, are installed sub-hori-zontally over the perimeter holes. Holes aredrilled using the development drillrig. Pre-reinforcement holes are 50 to 60 cm longerthan drifting length, to accommodate the3.6 m-long bolts. Inflation pressure is 300bars. Several variations of the method wereused to secure pillars and cuts in stopes.

With the Super Swellex bolts, produc-tivity actually increased to the same levelas for ramp and drift development in fair togood quality rock.

Since the few extra holes required forthe spiling bolts are drilled at the sametime as the blasting holes, and the bolts areinstalled in the short period betweendrilling and loading, this pre-reinforcementmethod does not increase the excavationcycle time. The experience was a total suc-cess, and the method became a standard atMine Doyon for bad ground conditions.Presently, around 300 m of access drift and

stope have been developed using thismethod. Close cooperation between theengineering and production departmentsmade this success possible.

MINING WORLDWIDE


Pre-reinforcement using Super Swellexat Mine Doyon, Canada.

Detailed Research in Peru

The Ares Gold and Silver Mine is located275 km north-west of Arequipa, Peru,nearly 5,000 m above sea level. It is a newore deposit in which the Victoria vein,nearly 2,000 m long and up to 200 m deep,is the main mineralized structure.

The design of drift support in the minehas been the subject of detailed research byits soil mechanics team, and different typesof bolts were field-tested.

The final choice, for both permanentand temporary support in the five differenttypes of rock at the mine, was Swellexbolts from Atlas Copco. Super Swellex andMidi Swellex bolts are being used in areaswhere the metal content is high and recov-ery must be around 95% and, in addition,some 1,600 Standard Swellex bolts/monthare being installed at the mine.

Thanks to its special features, theSwellex system has not only increasedsafety, but has contributed to an increasedadvance rate and improved economy.

Project: Underground gold and silver mine.Location: North-west of Arequipa, Peru.Excavation method: Drifting.Rock: Variety of different rocks.Rock reinforcement required: Permanent and temporary support.Rockbolt selected: Standard, Midi and Super Swellex.

Installing Swellex at Ares mine.

RR3/RC1.qxd 23/6/05 10:46 Page 65

MINING WORLDWIDE


Louvicourt Solution

The Louvicourt Mine is a polymetallic ore-body of copper, zinc, silver and gold,25 km east of Val d’Or in northwesternQuebec. It is a volcanogenic massive sul-phide deposit, starting 47.5 m belowground surface. It is part of the AbitibiGreenstone Belt, within the PrecambrianShield of eastern Canada. The orebodydips 70 degrees north and strikes E-N-E

with a plunge to the east. Dimensions ofthe orebody are 300 m along strike and500 m along dip. Thickness varies from20 m to 100 m. The mining method is longhole stoping with paste backfilling.

Systematic stability problems areencountered while drifting through faultzones disseminated in the orebody. Thegouge associated with the faults, theunfavourable dip of the two main jointsets, and the intense black chlorite alter-ation of the joints, contribute to the forma-tion of high roof and unstable groundconditions. Gouge thickness can reach upto 90 cm.

An efficient solution to this problem hasbeen to use Super Swellex bolts as a pre-reinforcement method. Three to four ringsof 3.6 m-long Super Swellex, on a 1.5 m x1.5 m to 2.0 m x 2.0 m pattern, areinstalled in the roof of the drift before thenext advance in the fault zone. The holesare drilled 50 degrees upward, and thebolts are inflated to 300 bars using a pneu-matic Swellex pump. Steel straps aresometimes used to increase support capacityand cohesion. The immediate supporteffect, and simplicity of the operation, with minimum handling, are definiteadvantages to using Swellex instead ofcable bolts.

The method creates a small increase in normal cycle time, but the drilling and installation time are more thanjustified by the cost, risk and lost timeassociated with rehabilitating a caved roof. The collaboration of the production depart-ment was crucial to developing themethod.

Such experience shows that Swellexbolts can be efficiently used as a pre-reinforcement system in order to improveproductivity and safety while excavatingtunnels in incompetent rock. The methodcan be applied to systematically supportroof, or to prevent caving from a nearbyfault zone. The method is fast, improvessafety, and can be easily integrated intodevelopment operations. Cooperation ofthe underground department for testing isparamount to the success of the technique,as the experience of the miners and super-visors is a valuable asset in improvingexcavation methods.

Project: Mine with copper, zinc, silver and gold.Location: Near Val d’Or, Quebec.Mining method: Longhole stoping with paste backfilling.Rock: Volcanogenic massive sulphide deposit.Rock reinforcement required: Support through fault zones.Rockbolt selected: Super Swellex.

Super Swellex aids safe and cost effective developmentat Louvicourt mine in Canada.

RR3/RC1.qxd 23/6/05 10:46 Page 66

Increased Output in Portugal

The Neves Corvo Copper Mine in southernPortugal, owned by Somincor, has recentlyincreased annual production from 2.1 to 2.3million t. Reserves are around 30 million t ofcopper and 1.9 million t of copper and tin ore.

Some 95% of the ore is being extractedusing several mining methods: 60% of thetonnage comes from a modified drift-and-fill method, 20% from benching, 10%from mini-benching, and the remaining10% from mining of the sill pillars.

Drift-and-fill mining is carried out by13 face drilling rigs, of which nine areAtlas Copco Boomer units. Two AtlasCopco Boltec rigs for mechanized rock-bolting, equipped with the latest Swellexhydraulic pumps, have been put into pro-duction, and the time taken to install aSwellex bolt in a pre-drilled hole at themine is now less than 30 seconds.

For benching and mini-benching, themine is using three drill rigs, two of whichare Atlas Copco Simba units.

The two fully-mechanized Boltec rigsare installing 2.4 m-long Standard Swellexbolts in the roof and walls of the orebodies,with an average spacing of 1 m. Swellexbolts have been used at the mine for manyyears, and more than 60,000 are installedannually. They are popular because theyoffer instant support with easy and fastinstallation.

Rockbolting is the bottleneck in the pro-duction cycle, and several bolting unitshave to be used because of the long dis-tances between the different faces,

The mine blasts 25 faces/day to meetproduction targets, which means time isprecious. Although the unit cost of Swellexbolts might seem expensive compared tosome other rockbolts, they have proved tobe the best solution in terms of the totalinstallation costs.

MINING WORLDWIDE


Project: Underground copper mine.Location: Southern Portugal.Mining method: Drift and fill with benching.Rock: Orebody roof and walls.Rock reinforcement required: Faster bolting to increaseproduction.Rockbolt selected: Swellex.

Systematic Support in Turkey

At the Çeltek Coal Mine in Turkey, some300 km north-east of the capital Ankara, thesupport system of a gate road has beenchanged from the traditional steel arches tosystematic support with Atlas Copco StandardSwellex EXL bolts. This follows a joint effortinvolving Atlas Copco Turkey and a team ledby rock support expert Professor Erdal Ünalof the Middle East Technical University. Theaim was to introduce the high load-carryingcapacity and yielding characteristics ofSwellex to the country’s coal industry.

A universal pull-tester developed byProfessor Ünal’s team was used to show thesuperiority of the Swellex bolts in terms ofspeed, safety and economy.

Time spent on roof support in a cycledecreased from two hours to between 20 and30 min/m of advance in the gate road, result-ing in an increased daily advance rate.

After experiencing the speed and easeof the Swellex bolt installation, the minemanagement and support crew agreed thatthe system also offers value for money. ■

Project: Underground coal mine.Location: Çeltek, Asia Minor, Turkey.Mining method: Longwall mining.Rock: Seam roof.Rock reinforcement required: Replace steel arches with bolts.Rockbolt selected: Standard Swellex EXL.

At the Neves Corvo copper mine inPortugal, Sven Buskqvist, WirsboStålrör AB, Antonio Rodrigues,Somincor, and Torres Marquez, AtlasCopco Portugal.

At Çeltek mine in Turkey, a Swellexbolt is installed to demonstrate itsunique ability to provide safe andimmediate support.

RR3/RC1.qxd 23/6/05 10:46 Page 67

RR3/68 24/6/05 15:13 Page 1

TUNNELS IN AUSTRIA


Second Tube for Graebern

The new 2.148 km-long tube was drivenparallel to the existing Graebern tunnel inhighly variable ground conditions. Thefaces at either end were in different strata,requiring a flexible approach to excavationand support.

The contractors used some equipment,such as the Atlas Copco Rocket Boomerdrillrigs, that was released following thecompletion of the 9.9 km-long Plabutschtunnel, a similar dualling project on the A9motorway at Graz.

Around 1.5 km of the tunnel was exca-vated to standard 70 sq m section, 400 m of which was in excavation class 7and needed a reinforced shotcrete or con-crete invert, requiring an enlarged sectionof 78 sq m.

An oversize safety section in the centreof the alignment provides a third lane overa distance of 48 m, where vehicles maypark in an emergency, or possibly turnaround. They may also turn to enter a widecross passage leading to the second tube,which is big enough for trucks.

South Attack

At the south end of the alignment, wherethe rock was generally too soft for blast-ing, an Atlas Copco two-boom RocketBoomer L2 C drilled for spiling and bolt-ing in the top heading, so that the facecould be mechanically excavated.

The area was intensively folded andfaulted, with a mixture of competent and

Atlas Copco Rocket Boomer L2 C atGraebern south face.

Removing Bottlenecks inAustriaCrossroads of EuropeWith its position in the heart ofCentral Europe, Austria serves as atransportation hub for virtually anybusiness needing to move goodsacross the continent.

For traffic between the BalkanStates and the north, or diagonallyacross Europe from east to south,Austria presents the shortest route.Indeed, the risk of traffic nuisance issuch that trucks are currently bannedfrom its highways during the nighthours.

In its efforts to upgrade to full European standards, Austria is build-ing more dual carriageways, anddriving parallel tunnels for a numberof existing bi-directional tunnels acrossthe country. In the tunnels, the latestin Atlas Copco technology is beingemployed, including the RocketBoomer L2 C and self drilling anchors.

Two such projects are the paralleltunnel recently completed at Graebern,on the Vienna to Klagenfurt section ofthe important A2 motorway whichconnects Vienna with Carinthia andItaly, and a twin tube tunnel project atSteinhaus, located near Semmering, afavourite skiing destination for theViennese.

Project: Parallel tube for existing bi-directional road tunnel.Location: Graebern, on A2 Vienna-Klagenfurt highway.Excavation method: Drill/blast and mechanical excavation.Contractor: Joint venture of Ostu Stettin, Hinteregger, and PorrTunnelbau.Rock: Mix of biotite gneiss and non-glaciated folded, faulted,and tectonised strata.Rock reinforcement requirement: Spiling followed byimmediate face support.Rockbolts selected: Super Swellex and self drilling anchors.

RR3/RC2.qxd 23/6/05 10:59 Page 69

TUNNELS IN AUSTRIA


incompetent rock. As there was no glacialcover during the past million years, glacial erosion did not remove the highlytectonised and incompetent parts present atthe southern portal.

The centre section of the top heading was generally left in place as a safety pillar, to support the tunnel face while sectional lattice arches were installedat 1.0-1.2 m centres, together withrockbolts and shotcrete. Part of the exca-vated face was also temporarily secured by 12 m-long self drilling anchors, which were grouted in place. For systemat-ic bolting, self drilling or cement groutedanchors with lengths of 4 m or 6 m wereused.

When required, 25 mm-diameter, 4 m-long pipe spiles were set around the roofprofile in 45 mm-diameter holes drilled bythe Rocket Boomer L2 C. Any blastholesrequired were drilled using 45 mm AtlasCopco Secoroc bits.

The top heading was followed by a 2.7m-high bench and invert, which were ex-cavated some 60-80 m back from the face,but periodically slipped back to 150 mbehind the face.

North FaceThe north end of Graebern featured biotitegneiss, a more-competent metamorphicsedimentary rock with a high amount ofquartz and feldspar. Predominantly, the rockmass was jointed and faulted, and so mostlydecomposed and friable. Therefore, spilingwith pipes was often an absolute necessity. Inaddition, Super Swellex 4 m-long bolts wereset in the roof at the face as immediate support.

Regular support comprised 15 cm ofshotcrete with one layer of wire mesh and4 m-long rockbolts. If spiling was re-quired, lattice arches were erected, andshotcreted in place. A three-boom semi-automatic Rocket Boomer L3 C performedthe support drilling duties at the north end,in addition to blasthole drilling.

Drilling of a full round of approximately130 x 2 m-deep holes in the top heading tookan hour, in addition to a half-hour for charg-ing and blasting. Blasting agents were dyna-mite and cartridged slurry, with 19 intervalsof electronic detonators with milliseconddelays at 80 milliseconds per step. Thedrilling rounds were set up using an array ofseven lasers to establish a perfect profile.

Steinhaus at SemmeringThe Steinhaus tunnel is on the B306 Vienna to Bruck road, which passesthrough Semmering, a favourite skiingresort for the Viennese. The B306 is beingupgraded, and will form part of the new S6highway. This will connect with the SanMiguel interchange on the section of theA9 Trans-European Highway between themain centres of Graz and Linz.

The tunnel is twin-tube and 1.5 km-long, on a double curving alignment that takes it into the side of the valley

in which the village of Steinhaus islocated. It has been constructed byBilfinger Berger for the Austrian highwaysauthority.

The rock quality is variable, generallysoft and non-glaciated, comprising chalk,phyllite, calcite and quartzite, with a maxi-mum cover of 60 m.

The tunnels accommodate a two-lanehighway in each direction. There are threecross-passages, with the middle one havinga large cross-section to facilitate theswitching of trucks between tubes in emer-gency situations.

Rock Support at Graebern Tunnel

RR3/RC2.qxd 23/6/05 10:59 Page 70

The full 80 sq m section of each maindrive was achieved with top heading,bench and invert excavations. The facespassed beneath some village houses witharound 50 m cover, and two blast vibrationmonitoring stations were set up.

Cautious Advance

Work at Steinhaus commenced at the westportal with a 47 m-long central pilottunnel, within which the pillar between thetwo main tubes was cast using self-com-pacting concrete. The separation over thefirst 50 m of alignment was 2 to 4 m,increasing progressively to 60 m at thehalfway mark. The rock pillar on thesecond 50 m of drive was anchored usingpre-stressed bolts, tightened by plates onboth sides.

The drillrig fleet comprised three late-series Atlas Copco Rocket Boomer 352S,and one newer Rocket Boomer L2 C. Theyspent 80% of their time drilling for rockreinforcement because, generally speaking,only 10-20 blast holes were required in thefaces of the top headings.

The faces, which were mechanicallyexcavated, were secured by up to nine 16ft-long self drilling anchors with mortarinjection. Roof and side support wasachieved mainly with grouted rebars andself drilling rockbolts from Atlas CopcoMAI, and five MAI M400 water mixingpumps were used for grouting.

In order to maintain reasonable under-foot conditions, a temporary shotcrete invertreinforced with steel mesh was laid in thetop headings, every 4 or 5 arches onadvance. Drainage holes were drilled in theface whenever necessary. Usually, three orfour arches were set at 1.5 m intervals ineach face during a 24 h cycle of three shifts.

Umbrella Working

At the 90 m mark on the south drive, a 20 m-high Karst cavity was encountered,which, fortunately for the tunnellers, provedto be dry. The drillrig was pulled back todrill over the face and into the cavity.

Some 30 cu m of 8 mm concrete wasthen pumped through the drillholes, usingone of the shotcrete jumbos. Advance overa 10 m stretch beneath the filled cavity wasprotected by arches of 20-30 spiles madeof 51 mm x 8 m-long R32 pipe installed at2 m increments.

Once into more competent ground, thedrillrigs were able to deliver 80-90holes/round in the top headings, drilled todepths of 1.5-1.7 m. Blasting was by mil-lisecond and long delay non-electric deto-nators and encapsulated slurry maincharge. The bench followewd at between 90 m and 220 m behind the face, where thetemporary invert was ripped out by an ex-cavator with hydraulic hammer. A concretepump was stationed at each bench as aconvenient way of pumping shotcrete pastthe ramp position, from where a mixertruck transported it to the face jumbo.

Self drilling rockbolts have becomevery popular in recent years, and are nowused in a number of different applications,for both surface and underground drilling.In tunnels, their primary use is for advancesupport of extremely friable rock, or informations where the drill hole will col-lapse before a normal rockbolt can be putin place.

The bolt is made up of five essentialparts: a threaded bolt, a single-usage drillbit, a connection casing, a screw plate anda nut. The rockbolts are available in stan-dard lengths, by the metre from 2-6 m-long, with special customer-designedlengths of up to 12 m. ■

TUNNELS IN AUSTRIA


Rocket Boomer 352S at Steinhausportal.

Project: Twin tube 1.5 km-long road tunnel.Location: Steinhaus on the B306 Vienna-Bruck road throughSemmering.Excavation method: Mechanical excavation with somedrill/blast.Contractor: Bilfinger Berger.Rock: Soft, non-glaciated chalk, phyllite, calcite and quartzite.Rock reinforcement requirement: Forward support andimmediate face support.Rockbolts selected: Self drilling Atlas Copco MAI rockbolts.

RR3/RC2.qxd 23/6/05 10:59 Page 71

Document2 3/10/05 12:12 Page 1

Performing in Permafrost

The Raglan mine is located on the remoteUngava Peninsula of northern Quebec,where the mean annual temperature isminus 10°C, with an ambient temperatureunderground of minus 15°C.

It is a conventional shovel-and-truckopen pit, with an underground mine atKatinniq, where there are two miningmethods in use: long-hole stoping and cutand fill.

Although large stopes are not typical atthe mine, a stope opened in 2003 measured160 m-long x 63 m-wide. The orebody iswide, with limited height and strike length,and the footwall dips at a 45° angle, making most of it unfavourablefor development of longhole stopes. At any given time, Katinniq has 10-15 stopesin operation, with only one or two being the more productive longhole stopes. The rest are cut-and-fill which,despite being more labour intensive,account for over half of the 50,000-55,000 t/month of ore produced.

Katinniq has reserves of 19.5 million t,grading 2.85% nickel and 0.79% copper,as well as significant recoverable cobaltand platinum-group metals. The mine isaccessible by air, and linked by an all-weather road to ship-loading facilities at

Deception Bay, about 100 km to the east.The nearest supply town is Rouyn-Noranda, about 1,600 km south.

With the ground permanently frozen toa depth of 425 m, rockbolting at Raglancould be a difficult and time-consumingprocedure, without Swellex. Although thecold makes working conditions difficult,the ground is more stable because there isno water moving through fissures in therock. The normal maximum stope size is30 m-wide and 105 m-long, so ground sta-bility is important.

The host rock is extremely competent,with no ground stress problems. With joint spacing over 2 m, the main rocksupport consideration is the risk of falling blocks. The mine generally uses 2.4 m bolts for stability, but these mayincrease to 4 m-long or 5 m-long boltswhen big blocks occur.

Previously, the mine used mechanicalbolts and rebar set in resin for rock sup-port. However, the mechanical boltsrequired periodic re-tensioning to be effec-tive. This was labour intensive, and the useof resin posed significant logistical andtransportation problems.

CANADA & JAPAN


Location of Raglan Mine in NorthernQuebec.

Swellex in Extreme TemperaturesHot and Cold MiningSwellex rockbolts are used success-fully in hot and cold extremes onboth sides of the world. Not only hasthe bolt been found to perform to fullcapacity in all temperature condi-tions, but it has also found favourwith the operators. Because of itslight weight, and speed of installa-tion, the operators are finding thatSwellex does not overexhaust themunder the rigorous conditions inwhich they work. Another bonus isthat grout mixes and resin ampoulesare not required, significantly reduc-ing the transportation costs toremote mines, and limiting the fetch-ing and carrying to be done underextreme conditions. This is truly amarket sector where Swellex isunbeatable!

Project: Raglan Katinniq nickel mine.Location: Northern Quebec, Canada.Mining methods: Longhole stoping, cut and fill.Operator: Falconbridge Nickel.Rock: Blocky with permanently frozen fissures.Rock reinforcement required: Long bolts not requiring resin.Rockbolt selected: Swellex Mn24 and Connectable.

RR3/RC3.qxd 23/6/05 11:01 Page 73

Hot Work in Hokkaido

Drillers at the Toyoha mine in Japan getmore than a warm welcome when theyarrive for work each day. Due to the vol-canic rock in the area, the mine generatesrock temperatures of 130°C, and a heat-wave follows the opening of any newareas. Humidity is extremely high, and it is not unusual to see jets of steamcoming from newly drilled rockbolt holes.These are, indeed, extreme conditionsunder which to install effective rockreinforcement!

Toyoha, which is the world’s largestproducer of the rare metal Indium from itslead and zinc operations, carries out sub-level stoping in the steeply inclined ore-body, where drifts are 3 m-high and 4 m-wide.

In these difficult conditions, and sinceneither cement grout nor resins can beeasily handled in such high temperatures,the mine uses Swellex rockbolts fromAtlas Copco for rock reinforcement.

Drilling and installation of 1.5 m-longSwellex bolts in the normal pattern used atthe Toyoha mine to stabilize a round isperformed by a single miner in just 32minutes. This is a very fast production rate,especially considering the high temperatureand humidity. The key is in the Swellexsystem itself, which enables bolt after boltto be expanded in just 22 seconds apiece.

The mine management insists that onlySwellex can give superior safety in hot

rock such as this, and rates the easy andtrouble-free installation system as a bigplus.

Toyoha uses up to 2,000 bolts/month ofthe 2 m-long Midi Swellex type, which arewell suited to the large diameter explosivesnow being used. The number of holesrequired at the face has been reduced as aresult.

The operators prefer Swellex boltsbecause they can be set in the hot condi-tions without using a work platform, orheavy tools and equipment. Two-thirds of the bolts currently used in the mine are Swellex. They are lightweight, easy,quick and safe to work with, and do notrequire grouting, keeping the work areaclean. ■

Easy InstallationAfter an extensive research and testingperiod, Raglan made the switch to Swellexbolts in 1999. Since then, they have beenusing Swellex almost exclusively, in orderto ensure consistent quality of rockboltingwhile maximizing productivity.

At Raglan, all drifts are screened and allstopes are bolted. The mine is budgeted touse: 6,500 of the 600 mm Swellex bolts for

fastening screens in the 5 m-wide drifts;50,000 of the 1.6 m bolts used largely inwall rock; 62,000 of the 2.5 m bolts usedfor the back; and 2,000 of the 3.8 m SuperSwellex bolts as needed.

Raglan uses brine to expand the Swellexbolts in order to avoid freezing problems.This has not resulted in detectable cor-rosion in the bolts, and recent pull testsconfirm this. Swellex Mn24 has nowreplaced Super Swellex at the mine.

CANADA & JAPAN


Installing Swellex at Toyoha Mine, Hokkaido, Japan.

Project: Toyoha lead/zinc mine.Location: Hokkaido, Japan.Mining method: Sublevel stoping.Rock: Volcanic host.Rock reinforcement required: Easily installed non-groutedrockbolts.Rockbolt selected: Standard and Midi Swellex.

RR3/RC3.qxd 23/6/05 11:01 Page 74

Support Investigation

A few years ago, owner Yxhult AB experi-enced a number of small falls of roof atKvarntorp mine. It was found that severalpoint anchor expander bolts installed in1968 had rusted through 0.8 m inside therock, and had fallen out.

The Swedish industrial safety authorityrequested Yxhult AB to launch an investi-gation to determine the extent of the prob-lem, and to recommend a rock supportprogramme that would ensure the safety ofpeople working underground.

The company contacted SvBeFo, theSwedish scientific organization involved instudying the behaviour of rock in mining,construction and building, to solicit theirinvolvement. The Stockholm-based con-sulting company Sycon was contracted tocarry out the investigation, and AtlasCopco agreed to take part in the project.

The ground water in Kvarntorp seepsthrough the overlaying shales, which haverelatively high sulphur content, and isknown to be corrosive. There was a con-siderable amount of water present in therock during the excavation of the openings,but this had disappeared over the years,

making it difficult to establish the exactconditions to which the bolts have beenexposed.

Rock Reinforcement

Support was exclusively by rockbolts,installed vertically as the drives and roomswere excavated. Expander type pointanchor bolts were used initially, then themine switched to cement-grouted rebar.These were used from 1967 to 1969, whenthey switched to resin-grouted rebar, andin 1987 to Atlas Copco Swellex bolts.

The following rock bolts and groutingagents were used during the productionphase of the mine: cement grouted rebar,2.2 m-long; resin-grouted rebar, 2.2 m-long, with two Celtite cartridges; resin-grouted rebar, 1.8 m-long, with two Celtitecartridges; and Coated Standard Swellex,1.8 m-long.

During this development of rock sup-port, point anchor expander bolts provedentirely inadequate, and were replaced bycement-grouted rebar. The disadvantage ofcement-grouted rebar is that it is messy,time-consuming, and does not provide anysupport before the cement hardens.

In 1969, the mine switched to resincartridges as the grout medium used toinstall rebar dowels. This has the advan-tage of providing more immediate support.

KVARNTORP, SWEDEN


Cross-section of bolt No 1 showscorrosion described as insignificant.

Coated Swellex ExaminedUnique TestingOpportunityNot far from Orebro in centralSweden lies Kvarntorp mine, a dis-used underground sandstone minethat has been converted as anarchive store.

The rock is sedimentary, occurringin horizontal layers, with sandstoneoverlain by shale. The sandstone isporous, but relatively homogeneous,varying from white to light grey incolour. It is lightly laminated withthin clay seams, which are often notmore than 1 mm-thick. The ground-water is corrosive, so, when CoatedSwellex rockbolts became available,the mine was quick to realize theadvantages, and began using them in1987. Recently, tests were conductedon two of these bolts that had beeninstalled nine years earlier, and it wasfound that virtually no corrosion hadtaken place.

RR3/RC4.qxd 23/6/05 11:09 Page 75

However, it is still arduous and, as withcement, there are high wastage factors.

Both resin and cement grouting of rebarpresent the operator with a number ofinstallation quality concerns. These rangefrom inadequate grout in the hole or, as inthe case of resin, “over-spin” or “under-spin”, both of which adversely affect thesupport capability of the installation.

Coated Swellex

Swellex rockbolts are manufactured fromfolded steel tubing that can be inserted inthe drill hole manually or mechanically,and expanded with high-pressure water.The installation takes a few seconds, andthe expanded bolt is pressed tightly againstthe rock, deforming to the irregular sidesof the drill hole. This provides guaranteedfull column support, as the water pressureis applied equally throughout the bolt.

Coated Swellex has a rubberized bitu-men coating on the outside of the bolt. Asthe bolt is expanded, this coating, which is semi-viscous, is pressed into themicrostructure of the rock on the inside ofthe drillhole. The coating provides a barri-er between the rock and the bolt that pre-vents the ingress of corrosive water. As thecoating completely covers the outside ofthe bolt, and the bolt expands over its fulllength, the result is a guaranteed qualityinstallation.

It was decided to perform pull tests on anumber of bolts at Kvarntorp mine to testtheir integrity after having been in the rock for nine years. The Swellex exceeded

their minimum specified breaking strengthduring these tests.

Overcored Bolts

It was then decided to over-core twoSwellex bolts to establish their condition.These were forwarded to the SwedishCorrosion Institute for further examination.

All Swellex rock bolts are stamped withan alpha-numerical identification. Therecovered bolts were marked 1.8 930125 BSTD Sweden, showing that this was a1.8 m-long bolt manufactured in Swedenon January 25, 1993. They were recoveredin mid-May, 2002, so were in the rock fora little over 9 years.

At the Corrosion Institute, the rock coreswere removed and the bolts visuallyinspected, after which cross-sectional pieceswere sawn out for more detailed inspection.

Observations by the investigating engi-neer were that uniform corrosion on theoutside of the bolts was very small, lessthan 0.1 mm-deep. Internal corrosion wasmostly non-existent, with a few small shal-low patches. One of the bolts had twosmall local corrosion penetrations that didnot affect the breaking strength.

Conclusion

The conclusion was that, after more thannine years in the corrosive environment ofKvarntorp mine, Coated Swellex bolts hadnot lost any of their strength or supportcapability. They were not involved in anyof the rock falls that had occurred.

Sycon made the following recommen-dation: the area where the rock falls hadoccurred should be re-bolted using 1.8 mCoated Swellex bolts fitted with 150 mm x150 mm bearing plates, installed 5bolts/row, with 2 m between each row.

The result of this investigation establishesCoated Swellex rock bolts as long term sup-port suitable for use in a variety of environ-ments. Situations differ from mine to mine,and from tunnel to tunnel, and require care-ful study by qualified people. However,there is no doubt that mines and tunnels withaggressive environments can benefit fromthe many advantages of Swellex rockbolts.

The full report from the SwedishCorrosion Institute is available from AtlasCopco in English upon request. ContactTurgay Ozan [email protected] ask for report number 80 103 (rev 1). ■

KVARNTORP, SWEDEN


Internal surface of bolt No 2 shows itis practically free from corrosion.

RR3/RC4.qxd 23/6/05 11:09 Page 76

Underground Laboratory

Yucca Mountain, located in the Nevadadesert approximately 160 km from LasVegas, is today the only site that the USDepartment of Energy (DoE) is studyingfor the nation’s first permanent high-levelnuclear waste repository.

The Exploratory Studies Facility (ESF),part of the Yucca Mountain project, will be

an underground laboratory for engineersand scientists to help determine the abilityof natural and engineered barriers to safelystore spent nuclear fuel and high-levelradioactive waste in a geologic repository.

A large percentage of the ESF tunneldesign has been done according to aNuclear Quality Assurance program (‘Q’-standard), similar to that used fornuclear power plants. Ground support is‘Q’ classified.

This has impact on ground supportdesign, type of ground support chosen,procurement of ground support products(including lifetime documentation andtraceability of materials used in manufac-turing), installation of ground support, and

NEVADA, USA


Curved drive at Yucca Mountain ESFtunnel, close to Las Vegas.

Tunnelling with Nuclear QualityAssuranceStability for aHundred YearsThe construction of the ExploratoryStudies Facility (ESF) at YuccaMountain has set new quality stan-dards for tunnelling operations. It hasbeen proved possible to build atunnel according to nuclear qualitystandards, while at the same timemaintaining flexibility for scientificinvestigations and acceptable tun-nelling productivity. The 7.8 km-longESF tunnel has been driven by TBMwithin the rock formation that isbeing evaluated to determine suit-ability for the final repository, andmay become a part of the repositoryitself.

The requirements on long-termstability for radiological safety of afuture repository, in this case equalto 100 years, resulted in rejection ofmost available ground support prod-ucts. Instead, Super Swellex rock-bolts were chosen, together withwelded mesh and a rolled steelchannel, for permanent support inthe ESF tunnel. A similar system was used to support the more recent 2.681 km-long East-WestCross Drift tunnel to investigateground conditions over the proposedrepository.

Tunnelling at Yucca Mountain will probably go on for many moreyears, adding invaluable practicalexperience to the world’s pool ofknowledge of how to constructrepositories for nuclear waste. Withnuclear waste accumulating in manyother countries, this project is beingwatched very closely by a number ofagencies around the world.

Project: Nuclear waste repository investigation.Location: Yucca Mountain, Nevada.Excavation method: TBM and roadheader.Contractor: Kiewit/Parsons Brinckerhoff.Rock: Volcanic tuff.Rock reinforcement required: Systematic roof support with 100year stability.Rockbolt selected: Super Swellex.

RR3/RC5.qxd 23/6/05 11:10 Page 77

verification of the function of the productsused.

A 7.8 km-long tunnel, which is a part ofthe ESF, has been completed. Investigationsto determine the suitability of YuccaMountain as a potential repository are wellunderway, following which a repositorylicence application will be submitted to theNuclear Regulatory Commission.

Exploratory Studies Facility

The 7.8 km-long, 7.6 m-diameter ESFtunnel was excavated by Kiewit/PB usinga CTS TBM to a design by TRWEnvironmental Safety Systems Inc. Byexamining the surface and the undergroundspace that will be accessed via the ESF, thescientists will be able to thoroughly inves-tigate rock strength and movement,groundwater, and earthquake and volcanicactivity.

Other factors that will be considered inthe site characterization include: geologichistory; geologic information; publicsafety and concerns; local economic andsocio-economic impacts; environmentalconcern; ease and cost of constructing andoperating the site; and the effect of hightemperatures on the strata.

The data gathered, together with resultsand conclusions from the investigations,will assist in the final decision on whetherYucca Mountain is suitable for a nuclearwaste repository.

Yucca Mountain consists of layers ofvolcanic tuff, with a total thickness of atleast 1.8 km. Most of the excavation willbe in the uppermost and middle TopopahSpring formations, located approximately300 m below the surface. This is the poten-tial subsurface repository horizon, and ismore than 100 m above the groundwatertable.

The ESF has been geologically mappedalong its total length, using a 55 m-longgantry built into the TBM trailing gear.

ESF Tunnelling Progress

The TBM was launched from a 60 m-longdrill/blast starter tunnel. The first part ofthe ESF tunnel, the North Ramp, wasdriven at a 2% downgrade against rockbeds dipping 2° to 15° to the east. The first200 m of tunnelling were difficult, andsteel sets were installed on 1.22 m centres.

The Bow Ridge Fault, encounteredapproximately 200 m into the mountain,was filled with a soil-like, weak tuffaceousmaterial, having an unconfined compres-sive strength as low as 1.4 MPa. Eventhough the fault had slipped approximately100 m, it was only a few metres wide.After crossing the fault, the TBM enteredsofter material in which steering was diffi-cult. Ground was lost above the TBM,necessitating backfilling and grouting ofthe void created.

For about 1,000 m, tunnelling wasthrough the Imbricate Fault Zone, whichproved very difficult. Minor faultingevents had caused through-going joints,oriented in the same direction, closelyspaced and nearly parallel. This, in combi-nation with low stressed rock, led to blockfallouts, and steel sets combined with steellagging had to be used extensively.

Close to the Ghost Dance Fault, twotesting alcoves were excavated to gainaccess to the fault deep inside YuccaMountain.

After approximately 2,700 m of tun-nelling from the entrance at the NorthPortal, the TBM reached the TopopahSpring potential repository host rock atapproximately 300 m depth. In this forma-tion, 3,000 m of the ESF main tunnel was

NEVADA, USA


Part of the ESF main tunnel withtypical ground support installed.

RR3/RC5.qxd 23/6/05 11:10 Page 78

constructed using Swellex bolts, wire meshand rolled steel channels for support, andhigh advance rates were achieved.

NQA System Applied toGround Support

Since the ESF is an underground labora-tory, where rock characteristics are studied,the DoE stresses that ground support mustnot interfere with the geotechnical andgeological testing. Also, the final groundsupport system must be installed as thetunnel progresses.

The tunnel must be reinforced in such away that stored nuclear waste could beretrieved 100 years after it is put in place.Hence, the ground support must ensurelong-term stability and maintainability.

Cement grouted rebar bolts cannot beused in areas where scientific investiga-tions will take place, because the groutmay penetrate rock fractures and contami-nate test results. Also, due to the curingtime of the grout, this type of bolt cannotbe tested immediately after installation.

There is also a ban on the use of epoxyresin based rockbolting systems, since theamount of organic material in the tunnelhas to be minimized in order not to poseany threat to nuclear waste packages.

The use of shotcrete is limited, since itcan interfere with geological mapping andgeochemical tests.

For many such reasons, Swellex rock-bolts, manufactured by Atlas Copco, wereapproved for permanent rock reinforce-ment in the ESF tunnel.

Procurement of ground support materi-als requires lifetime documentation andtraceability, from materials used in themanufacturing, to fully inspected installa-tions. Records are kept in a thorough andprecise way, and internal and externalaudits are carried out to certify that every-thing is done according to specificationsand procedures.

Ground Support System

As main support, 3 m-long Super Swellexbolts complete with the domed SuperSwellex face plate on a 1.5 to 1 m pattern,depending on ground conditions, wereused, together with a 250 mm rolled steelchannel and welded wire fabric (WWF).The steel channel and WWF prevent rocksfalling from the roof of the tunnel. In addi-

tion to this, steel reinforced concreteinverts were installed as the TBMadvanced, providing the surface and trackto support the TBM trailing gear.

About 70% of the tunnel has been sup-ported by Super Swellex rockbolts, withsteel sets used for the remaining 30%.More than 20,000 Super Swellex boltshave been installed in the ESF tunnel.

The Super Swellex rockbolt is a frictionbolt manufactured by Atlas Copco. Thebolt is made from a welded circular steeltube, then folded on itself into a ‘W’-shapeto decrease the diameter. Bushings are thenpressed onto the collapsed steel tube, andthe ends sealed by welding, to create a

NEVADA, USA


Each steel set and position for theSuper Swellex bolts has a number, forthe installation report.

Installing Atlas Copco Super Swellexfrom the TBM bolting station incompetent ground.

RR3/RC5.qxd 23/6/05 11:10 Page 79

confined space inside the bolt. A hole isthen drilled in the lower bushing. Whenthe bolt has been positioned in the bore-hole, water is injected through the holedrilled in the bushing, causing the tube tounfold. At 30 Mpa the bolt is full expandedin the hole, and the pump automaticallystops. As the pressure inside the boltreaches 30 Mpa, the steel tubing adapts tothe shape of the borehole, and may consol-idate the surrounding material while itexpands to fit the irregularities of the hole.The resulting frictional and mechanicalinterlocking reinforces and increases thestability of the rock surrounding the drilledhole.

When each batch of bolts arrived at site,the Kiewit/PB Quality Control group car-ried out thorough tests and inspections toverify that they had not been contaminatedor damaged, and that the dimensions wereaccording to the specifications.

Rockbolt drilling and installation wascarried out at two stations on the TBM. Atthe first station, four Swellex bolts wereinstalled, together with the screen and thechannel. At the second station three holeswere drilled, and the remaining three boltsinstalled, including the bolt located at thehighest point in the tunnel. The nominal

spacing was 1,500 mm, with allowablemaximum of 1,687 mm. Spacing and pres-surization of the bolts was monitored toverify that they were properly installed,with a pressure between 290 and 310 bar.

The Swellex pump unit was checkedwith a calibrated gauge at least once a dayby the Shift Engineer to ensure that thepump was giving the correct pressure.

During tunnelling, five out of every 100rockbolts installed were tested to check ifthe proof load was reached.

If the TBM entered a new geologicalformation, five destructive pull-tests werecarried out to verify that the Swellex boltsmet the minimum anchoring requirement.

Complementary to this, 20 non-destruc-tive pull-test were made. Not a single boltfailed in the pull-out tests.

Future Tunnelling

Further tunnelling since completion of theESF tunnel has included the 2.681 km-longexploratory East-West Cross Drift Tunnelacross the potential repository. Thisemployed a 5 m-diameter Robbins hard-rock TBM, which started at an intersectionwith the North Ramp of the ESF and, afteran initial curve, followed a tangentialalignment, and crossed over the proposedrepository block west of the main loop ofthe ESF tunnel, to terminate in theTopopah Springs geological formation.

Once again, Super Swellex 1.8 m-longrockbolts were used for ground support ona 1.2 m x 1.2 m grid over the full crown,with welded wire mesh and 1.2 m-longsteel channels. A total of 20 steel sets wasrequired in only one area of the tunnel,where the Super Swellex bolts could notprovide long-term support. The TBM aver-age advance was 25 m/day over 106mining days, with a best shift of 34.6 m,best day of 73.2 m, and best week of 266.7 m. The TBM was mining for only25% of the time, due to the concurrentscientific and environmental experimentsbeing carried out.

The design of the repository is not yetfinalized. However, a system of tunnelstotalling more than 200 km is beingdiscussed in which more than 1 million boltswill be installed over a period of 20 years.

Following the signing of the YuccaMountain Resolution on 23rd July, 2002,the Nuclear Regulatory Commission is con-sidering licensing the repository. ■

NEVADA, USA


Using the drill feed to press the screenagainst the rock while installing aSwellex rockbolt.

RR3/RC5.qxd 23/6/05 11:10 Page 80

Driving from Dresden toPrague

The new 200 km-long A17 autobahn underconstruction from Prague in the CzechRepublic to Dresden in eastern Germanywill provide the Czech capital with rapidaccess to northern Europe and the NorthSea ports, and will also form a vital sectionof the Trans-European road network.

The most difficult part of this section isthe 8.85 km-long alignment from Gorbitzto Sudvorstadt, where contractor WalterBau undertook the twin-tube, three-lane1.1 km-long Doelzschen and the 2.3 km-long Coschutz tunnels using sequentialexcavation techniques.

Both tunnel alignments are predomi-nantly in syenite, a hard rock with around10% quartz content. They were each

TUNNELS WORLDWIDE


Atlas Copco Rocket Boomer 352 umbrella drilling at Dresden.

Swellex Versatility in TunnellingFast Installation andImmediate SupportSince the introduction of the AtlasCopco COP series of high-performancerock drills, drilling is no longer neces-sarily the bottleneck in tunnellingoperations. Mounted on sophisticat-ed rigs, drilling preset hole patternswith contour and profile control,these machines have encouragedtheir owners to reappraise everyaspect of the face operation.

Inevitably, focus has been broughtto bear on the rock reinforcementsystems in use, and their impact onoverall productivity. Fast drilling andslow rockbolting rarely make eco-nomic sense, not least becauseexpensive equipment may be under-utilized, while conditions are madesafe.

In this environment, Swellex boltscome into their own, as the mostcost-effective solution. They are fastto install, and give immediate sup-port, making the face available forfurther operations in the shortestpossible time. The following casestudies trace this theme, through dif-ficult motorway tunnels in Germanyand Spain, fast-advancing railwaytunnels in China and Switzerland,and in the new road system on thevolcanic Atlantic island of Madeira.

Project: 1.1 km and 2.3 km twin tube, three-lane road tunnels,150 sq m section.Location: Motorway between Germany and Czech Republic.Excavation method: Drill/blast, top heading and benching. Contractor: Walter Bau.Rock: Syenite, fractured and weathered in places.Rock reinforcement requirement: Immediate support, due tolarge span.Rockbolt selected: Super Swellex, and Boodex close to theportals.

RR3/RC6.QXD 23/6/05 11:12 Page 81

driven by drill/blast in a single directionfrom twin portals.

Top headings of 72 sq m section preced-ed the benches, advancing mainly in soft,mixed ground requiring a lot of support.The full, flattened ovoid section of 150 sq m was achieved with a 41 sq mfollowing bench, and a 37 sq m invert.

A total of eight Atlas Copco Boomer352 drillrigs were used for face drilling,rockbolting, and umbrella drilling. Facedrilling in the top headings was undertakenby two Atlas Copco 352 Boomers, stand-ing side by side. The added flexibility ofthe two-rig system speeded up the drillingand charging process, to the extent that theentire excavation cycle could be completedin 2.5 h. This facilitated up to four roundsin each 24 h period, leaving 14 h availablefor support work and rock reinforcement,much of which was scheduled for the nightshift.

Heavy-gauge steel arches were set inthe top headings, with two layers of Q378steel mesh and two applications of shot-crete to roof, sides and floor. A row of 4 m-long Swellex rockbolts was set in a 22 m-long radial arch at the face to give

early support, and 5% of these were ran-domly tested at 10 t pulling pressure, as aroutine stipulated in the contract.

Where immediate support is required,Swellex rockbolts can be in place and pro-viding full support up to seven hoursearlier than conventional cement groutedbolts. This was invaluable in the softerground towards the ends of the tunnels,where pattern rockbolting was used.Elsewhere, in better rock conditions, thecontractor favoured the system becauseSwellex bolts are fast to install and offerguaranteed support. The consistent use oftop specification rockbolts was reckoned toimprove the overall quality and integrity ofthe tunnel.

When the ground got too soft for con-ventional excavation, two Atlas CopcoBoomer 352 machines equipped with drill-rod cassettes were available. These drilled15 m-long holes around the periphery ofthe crown, using Odex eccentric bits andextension drillrods. The holes were thenlined with perforated steel tubes, throughwhich cement grout was pumped to form aprotective umbrella. Beneath this umbrella,a 12 m advance could safely be made.

TUNNELS WORLDWIDE


Fast Bolt for Madeira

The chain of mountain peaks that formsthe Madeira Islands, an autonomousPortuguese region with its own govern-ment, rises some 5,300 m from the bed ofthe Atlantic Ocean. Madeira is the largestisland of the archipelago, and is 57 km-long and 22 km-wide. It has a populationof around 260,000, of whom 120,000 livein the capital, Funchal. The islands arelocated 545 km from the coast of northAfrica, having been formed by volcaniceruption. The resulting mountains aresteep, and plunge from elevations of

1,800 m into deep valleys. Roads are tortu-ous and often dangerous, and travelling isfraught with problems. Inland routes areslow and winding, and the coastal roadsare fringed by high cliffs, and are prone torock falls caused by winter floods from themountains.

Tunnels have been employed to carrythe roads beneath the mountains and underthe cliffs, levelling the routes and makingthem safer. The picturesque Via Rapidaroad from the airport to the capital Funchalis a typical example, running over bridgesand through 22 tunnels, with a further sixto be constructed.

The new Via Rapida tunnels were builtby three contractors: Zagope; Tamega; andAvelino Farinha & Agrela. Rocket Boomer104 and 135 drillrigs were used, two of atotal of eleven Rocket Boomer rigs that areemployed on tunnelling projects inMadeira. Atlas Copco Swellex rockboltsare also a favourite reinforcement methodin the typical strata of volcanic basalt andtuff.

The Porto Moniz project, near SãoVicente, comprised five tunnels up to1,269 m-long. It was designed to divert

Project: A dozen km-long road tunnels, each around 60 sq msection.Location: Madeira Island, a self-governing region of Portugal.Excavation method: Drill/blast, mostly at full section.Contractors: Zagope, Tamega, Epos, and Avelino Farinha &Agrela.Rock: Volcanic formations with lava streams, fractured basalt,ashes and tuff. Rock reinforcement requirement: Versatile system to cope withextremely irregular geology.Rockbolt selected: Standard Swellex.

RR3/RC6.QXD 23/6/05 11:12 Page 82

heavy traffic from the scenic coastal roadthat runs under the cliffs by the ocean. Thisis a dangerous route, not least because ofrock falls and floods. Portuguese contrac-tor Tecnorocha used three of their fleet ofnine Atlas Copco Boomer drill rigsequipped with COP 1238 rock drills todevelop the tunnels. Blastholes were 4.2 m-deep, and advance varied between3.5 m and 4 m/blast, resulting in an aver-age advance of 7 m/24 h.

Standard Swellex rockbolts, togetherwith mesh and shotcrete, provided the per-manent support, because they proved to bethe most cost-effective solution. The speedof installation enabled Tecnorocha to finishthe project sooner, and utilize their equip-ment more efficiently.

The Ecumeada Tunnel, built through theSerra de Agua mountain in the centre ofthe island, is the longest single tunnel at3.1 km, and has cut driving time from thenorth to the south coast by 20 minutes,making the journey much safer.

Contractor EPOS excavated the tunnelby drill and blast, using Standard Swellexrockbolts, together with steel fibre rein-forced shotcrete when the rock was goodenough, and steel arches, together withwire mesh and shotcrete, when it was not.The volcanic rock formations are prone tochange very quickly, and heavy waterinflows were often experienced. The geo-technical engineer reported that theSwellex bolts proved very quick and easyto install, and provided good reinforcementin the constantly changing rock conditions.

Ponta do Sol was a project comprisingthree road tunnels, with a total length of1,900 m, where Avelino Farinha & Agrelaused an Atlas Copco Boomer 352 fordrilling the blast holes and bolt holes.Rock reinforcement comprised Swellexrockbolts, wire mesh and shotcrete. A

Boomer 352 installed 15 bolts/h with apneumatic Swellex pump, and up to 30bolts/h using a hydraulic pump.

Very large water inflows were experi-enced, and a waterproof plastic membranewas installed prior to the final 25 cm-thick,cast-in-place concrete lining. The heads ofall bolts were cut away to provide an evensurface for the membrane.

TUNNELS WORLDWIDE


Porto Moniz, Madeira, wheretopography favours tunnels as ameans of shortening distances.

Hong Kong Cannot Wait

Major new tunnelling operations in HongKong have used Atlas Copco drilling andbolting equipment fitted with the verylatest computerized capabilities, togetherwith Swellex rockbolts and full serviceback-up agreements.

The 5.5 km, 110 sq m Tai Lam tunnelon the West Rail development was aNishimatsu-Dragages joint venture, withthe two contractors driving the single

Projects: Tai Lam tunnel–West Rail, 5.5 km, 110 sq m. Black Hilland Pak Shing Kok tunnels, 20.5 km on the MTRC (metro), 80 sq m.Location: Hong Kong, China.Excavation method: Drill/blast, full section.Contractors: Nishimatsu-Dragages joint venture, Dumez.Rock: Mainly hard rock, such as granite. Rock reinforcement requirement: High productivity systems tospeed up excavation.Rockbolt selected: Standard Swellex.

RR3/RC6.QXD 23/6/05 11:12 Page 83

tunnel from opposite ends. Nishimatsu’sstretch was 2.6 km-long, and they achievedan average advance of 200 m/month withRocket Boomer WL3 C rigs. Their bestmonthly performance was 230 m, with twoblasts/day, using the fully-automated ABCmode for 80% of the time.

Atlas Copco agreed a drillmetre con-tract linked to spare parts and rock drillingtools supply, as well as an around-the-clock service arrangement.

The Black Hill and Pak Shing Koktunnel projects on the MTRC TseungKwan O Extension are part of a 12.5 km-

long, five-station extension which willserve a population of 340,000. A majorfactor in the progress of both projects wasthe performance of six Atlas Copco L2 CRocket Boomer rigs.

The Black Hill tunnels total 8 km, withfour tunnels designed to serve the up anddown trains of two MTR lines, and acentre siding. Here, six junction chambers,and two crossovers with 80 sq m cross sec-tions, were excavated by joint venture con-tractors Dumez of France and Chun Wo ofHong Kong.

The contractor used three new RocketBoomer L2 C rigs for face drilling, andtwo second-hand Boomer 281 units forrockbolting. The rigs drilled 4.6 m rounds,and some 30 m/day were achieved for allfour tunnels, with a best daily advance fora single face of more than 12 m.

The Pak Shing Kok tunnels project wasalso a complex job, with nine tunnelstotalling 6.4 km built by a jv of Hyundaiand Kier International. Tunnelling was car-ried out in a mixture of volcanic tuff andgranite, using three Rocket Boomer L2 Cdrillrigs with two booms, drilling to adepth of 4.2 m. Poor rock areas requiredaround 60,000 cu m of fibre-reinforcedshotcrete, and some 5,000 Atlas CopcoSwellex rockbolts. Swellex was chosenprimarily for its fast installation time ofaround one minute, compared to the 10-15minutes for conventional bolts.

Although the tunnels are amongst themost complicated on the MTR, the con-tractor was able to maintain an averageprogress of 550 m/month, completing thejob in less than a year, compared to theforecast of 18 months.

TUNNELS WORLDWIDE


Rocket Boomers WL3 C drillingrockbolt holes at Tai Lam in HongKong.

Holding Fast on SlippingGround

In Spain, the Autovia del Cantabrícomotorway will eventually run some 500 km along the coast of the Bay of

Biscay, from San Sebastian in the east toLa Coruña in the west, linking the cities ofBilbao, Santander, Oviedo, Gijón and LaCoruña. The project and works promoter isthe Ministry of Public Works. Parts of theeastern section are already open to traffic.Other sections, like the 65 km-long stretchfrom Ribadesella to Gijón, are underconstruction.

The 1.3 km-long El Fabar twin tubes, inpredominantly fractured limestone with slateand quartzite, were driven by a jv of FCCand Dragados using Atlas Copco RocketBoomer L2 C drillrigs on each face. ThreeAtlas Copco Wagner ST 8A Scooptramswere employed shifting the muck.

Project: 1.3 km El Fabar, twin tube road tunnel. Location: Northern Spain Excavation method: Drill/blast, top heading and bench.Contractor: Joint venture Dragados and FCC.Rock: Weak strata of slates and fractured limestone. Rock reinforcement requirement: Anchorage capacity, even inclay-bearing formations.Rockbolt selected: Standard Swellex.

RR3/RC6.QXD 23/6/05 11:12 Page 84

The 54 sq m top headings were drivensome 700 m from the east end, then thewhole operation moved to the west portals.The top headings were holed through inthe middle of the tunnel before benchexcavation started. The Scooptrams werefully effective at this range and section,enabling the normal number of load/hauloperators to be halved.

The Boomer L2 C units drilled 40-50blastholes per round, with the fracturedrock limiting depth to 1.5 m, and steel archsupport with mesh and reinforced concretewas required. For every metre of advance,ten 3.6 m Swellex rockbolts were installedfor instant support, in holes drilled by theBoomer rigs.

A 24 h/day, 6 day/week schedule wasoperated at the site, with the average dailyadvance 4 m on each face.

TUNNELS WORLDWIDE


Rocket Boomer L2 C in top heading at El Fabar.

AlpTransit, Largest EuropeanTunnelling Project

Lotschberg was being driven from thesouth by a 9.38 m-diameter TBM from theRaron portal and a similar machine fromthe Steg lateral adit. Both of these weregripper TBMs, each equipped with workplatforms with anchor drills immediatelybehind the face. Rockbolting and meshingwas undertaken 4.2 m behind the cutter-head, and this is followed by independentlyoperated shotcrete robots, which sprayed aconcrete lining over the crown. YieldingSwellex was installed to counter expectedproblems of rockburst, caused by theincreased overburden in competent gneiss.In rockburst, the pressure builds up in therock around the tunnel perimeter, and canyield explosively, causing dangerousspalling. If the rockbolt is designed to takeup some of this swelling pressure, then thebursting effect can be mitigated withoutcompromising on support.

Experience gained at Raron has beenused to develop the new SwellexManganese Line, which offers more load-ing capacity and enhanced elongation.COP 1432 rock drills speeded up thedrilling, and the easy and fast installationof the Swellex bolts provided immediatesupport behind the TBM. The TBMsadvanced an average of around 90 m/week.

Operations in the north were concentrat-ed at the lateral adit at Mitholz, from wheretwo faces were driven south, and one north,using Atlas Copco Rocket Boomer XL3 Cthree-boom rigs. These are each followedby a suspended trailing backup carryingtransformers, cable reels, ventilation fansand ancillary equipment. A full 8 m-wide x8.5 m-high face was drilled to 4.5 m depthfor each blast. During and after muckingout, the blasted area was mechanicallyscaled, and the roof and sides were shot-creted. Some 20-30 Swellex 3 m or 4 mrockbolts were then installed into holes

Projects: Gotthard base tunnel, 57 km; Lotschberg base tunnel,34 km.Location: SwitzerlandExcavation method: Drill/blast, full section and top heading;TBM 9.43 m diameter.Contractors: Satco jv (Mitholz), MaTrans jv (Raron), Ast-Holzmann (Amsteg).Designers: Consortium of best Swiss engineering andconsulting companies. Rock: Mainly hard rock such as granite, limestone, schist,gneiss, granodiorite, amphibolite. Rock reinforcement requirement: Safety; versatility to copewith geology and load requirements; high productivity withdrill/blast and TBM; some rock bolts have to withstand rockbursts.Rockbolts selected: Standard Swellex, Super Swellex, YieldingSuper Swellex.

RR3/RC6.QXD 23/6/05 11:12 Page 85

drilled by the Boomer XL3 C. In squeezingground, wire mesh and fibre reinforcedshotcrete were used, and, in the extremesouth of the drive, where crystalline rockmay produce rockbursts, SwellexManganese and MAI SDA were used.

At Alptransit Gotthard, contractor AstHolzmann completed the 1.78 km Amstegaccess adit on a 1% downgrade through theAar Massiv and Erstfeld gneiss to the maintunnel horizon, where four faces wereestablished.

An Atlas Copco Rocket Boomer 353Edrillrig was used on the adit to drill a fullface of 105-110 holes to an average 3.5 mdepth. The face took around 1 h 50 min todrill out, and the holes were charged withaluminized slurry with non-electric detona-tion. Average daily advance was 10 m, orfour rounds.

Swellex rockbolts of lengths 3 m or 4 mwere installed into holes drilled by theBoomer 353E, using the rig basket foraccess. Following each second round ofadvance, a 5 cm layer of shotcrete wasapplied to the roof. A further 5 cm of fibre-reinforced shotcrete was then applied tothe walls, and another 2 cm to the roof.

At the base of the adit, a 90 m-long x 13 m-wide x 12.5 m-high transformerroom was excavated, again using theRocket Boomer. This was advanced as an8.5 m-high top heading and 4 m bench tocreate a 125 sq m cross-section, reducingto 108 sq m at the back. Most of the sup-port was by 3 m and 4 m-long Swellex setin 38 mm holes.

The junction with the running tunnels ishugely impressive, particularly in view ofthe 1,000 m of overburden at this point.The profile of the running tunnels was nearperfect, with average overbreak of 18-22 cm measured by the Bever profileron the drillrig.

Two 9.58 m TBMs started on the 11.4 km drives towards Sedrun in mid-2003, with 40 m-long crosspassages at 320 m intervals.

In the opposite direction, excavationtowards the portals has not yet started.Meantime, Murer and Strabag have drivena 1.88 km-long cable tunnel between thetransformer room and the existing Amstegpower station using a Robbins 3.7 m-diam-eter hardrock TBM.

Swellex has a prominent role inAlpTransit, since Swiss designers can relyon the safety and controllability of itsinstallation, as well as its versatility, whichis particularly important in long and deeptunnels. Contractors are happy thatSwellex is a good investment, improvingproductivity and helping to keep costsunder control. ■

TUNNELS WORLDWIDE


Atlas Copco Rocket Boomer XL3 C, oneof three delivered to Mitholz.

Mountain of Swellex at Mitholz onAlpTransit Lotschberg.

RR3/RC6.QXD 23/6/05 11:12 Page 86

Alassio Motorway Link Road

Ilbau, a division of Austrian contractorStrabag, has excavated a total of over100 km of TBM tunnels, of which morethan 50 km are in Italy. The companyemployed its veteran 3.6 m-diameter JarvaMk12 TBM to excavate the pilot for the2.4 km-long two-lane road tunnel on a newlink road between Alassio and the nearbyGenoa-Firenze motorway. The four-lanehighway was built in the 1960s, and passesthrough many tunnels and over manybridges on its route parallel with the Italiancoast. As with all TBM projects, the aim atAlassio was to install adequate supportwith minimum impact on TBM productivity.

With a stroke of 1.2 m and a cutterheadbody of about 2 m, the Jarva TBM allowedinstallation of immediate support within3 m of the face. However, since thisinvolved TBM downtime, it was kept to aminimum, with most support work carriedout concurrent with TBM advance fromthe platform on the trailing backup some16 m back. This also allowed installationof truly radial rockbolts in the crown.

ITALIAN TBM APPLICATIONS


Ground support by rock classificationbehind a TBM.

Rapid Support Behind the TBMImproving UtilizationFor TBM tunnelling, the Alpine andAppenninic geology of Italy is bothgood and bad. The relatively hardrock suits TBM tunnelling, butvolcanic and seismic activity over the millennia has rendered it highlyfractured and disturbed, requiring arelatively high degree of support.TBM utilization in Italy can be as lowas 30% to 50%, with rock supportand reinforcement accounting for50%, or more, of the total productiontime.

When rock support is required inconjunction with a TBM operation,consideration must be given to the type of support required, andhow quickly it can be installed. Inhighly fractured rock, reinforcement,principally rockbolts, should beinstalled as quickly, and as close to the face, as possible. However, for most types of TBM, installingsupport close to the face results in downtime. Given the relativelyhigh cost/m of TBM tunnelling, such stoppages are a major concernfor both the contractor and the client. Developments in the speedand ease with which support can be applied to improve TBM utiliza-tion are of interest to all partiesinvolved in TBM tunnelling in dis-turbed rock. The main challenge is tolimit machine downtime and increaseproductivity while at all timesrespecting safety requirements. AtAlassio, the client specified Swellexand supplied a stock of bolts to thecontractor, such was the interest inimproving TBM utilization.

Project: Pilot tunnel for motorway link road.Location: Alassio, Italy.Excavation method: Open face TBM.Contractor: Ilbau srl.Rock: Soft, dry, non-abrasive calacareous marls, some clay andblocky rocks.Rock reinforcement required: Fast, dependable roof supportwith five-year life.Rockbolt selected: Swellex.

RR3/RC7.qxd 23/6/05 11:13 Page 87

As part of its contract, Ilbau was respon-sible for the design of the pilot tunnel sup-port. For more reliable estimating, andeasier communication with its client, Ilbaudeveloped a rock class and support mea-surement system specifically for TBM tun-nelling (Table 1). Adapted from establishedAustrian practice, the table not only consid-ers the most appropriate rock support forgiven rock conditions, but also specifieswhere, and how quickly, the support shouldbe installed. In better rock conditions(Classes F1, F2 and F3) bolts, mesh andshotcrete could be installed from the work-ing platform without interrupting TBMprogress. In Classes F4, F5 and F6, supportmust be installed as close to the face as pos-sible, and requires a halt in TBM advance.

Class F7 constitutes rock with no self-supporting capacity. In such conditions,ground consolidation techniques, or fulllining support with ribs and timber laggingor bolted liner plates, may be required. Inzones of extremely difficult ground, con-solidation and support measures ahead ofthe TBM should be considered.

At Alassio, because of the potentialimpact on TBM utilization, the paymentschedule for rockbolting and other supportrequirements varied according to where itwas installed, with higher unit prices forsupport installed close to the face, involv-ing TBM downtime.

The client specified the use of Swellexfor rock reinforcement at Alassio, and sup-plied the requisite bolts to Ilbau for installa-tion. Although sometimes perceived as moreexpensive than alternative rock support andreinforcement systems, the unit price ofSwellex becomes substantially less signifi-cant when compared with the costs saved inlabour and TBM downtime. The easy han-dling of Swellex is welcomed by tunnellingcrews, and its geomechanical properties andspeed of installation are attractive to consult-ing engineers, clients and contractors.

Alassio geology comprises mainly soft,dry, non-abrasive calcareous marls with

defined bedding, some clay content, andzones of fractured and blocky rock. Rockquality tends to change very rapidly, andoften from stroke to stroke of the TBM.

As a rock reinforcing tool, Swellex iseffective over a particularly wide range ofrock and soil types. In Ilbau’s table of rocksupport for instance, Swellex is applicablein all classes requiring rock bolts, fromclass F1 to F6. By specifying Swellex, thereis no need to keep a stock of any other typeof bolt on site. Together with its ease ofapplication and immediate support poten-tial, Swellex has the all-round advantage.

In the first 1,918 m of the Alassio pilottunnel, required support was mostly that oftypes F2 to F4, with 15% in type F5. Swellexreinforcement over the same length averagedabout four bolts/linear metre, 60% of whichwere 1.5 m-long, and the remainder 2.1 m.Support installed was about 10% more thanoriginally estimated, with a corresponding10% reduction in productivity.

Swellex, wire mesh and shotcrete wereused in fault zones where roof falls hadoccurred. In other areas, thin layers of shot-crete spalled off, with small falls of rockaway from bedding planes. These created noserious safety hazards, and confirmed thatIlbau was installing adequate support for apilot tunnel, neither too much, nor too little.

Rock support accounted for approxi-mately 50% of TBM downtime on theAlassio pilot tunnel, with most falling intosupport types F2 to F4, and 15% in type F5.

To monitor the quantity and quality ofsupport installed, the client’s consultantgeologist visited the site about twice aweek. In addition, the consultant monitoredgeotechnical instrumentation installed byIlbau. Along the tunnel there were 15 con-vergence measuring stations, and three sta-tions containing three groups of 1.5 m, 3 m,and 4.5 m long extensometers in the crownand into each wall, as well as five tangen-tial and five radial pressure cells. Datagathered greatly assisted the main tunnelfinal support and lining designs.

The TBM completed the 2,472 m-longpilot tunnel in eight months, working127 h/week on a 2 x 11 h shift/day, 5.5days/week, and broke through on schedule.Average advance was about 15 m/day, witha best advance of 53 m/day in class 2 rock,installing 110 bolts, mainly from the backupplatform. This was close to the optimum60 m/day achievable in a short tunnel oper-ating a single track muck hauling system.



Table 1. Comparison of rock classifications methods.

Class Bieniawski 1973 Deere 1969 Barton 1974 O-Norm

RMR RQD Q Class (3.9 m dia. TBM)

I 83 90 33.0 F1-F2II 67 75-90 12.5 F3III 52 50-90 8.5 F4IV 29 25-50 1.5 F5V 15 less than 25 0.09 F6

RR3/RC7.qxd 23/6/05 11:13 Page 88

Val d’Arzino Water Diversion

The Val d’Arzino is north of Venice, nearthe border with Slovenia and Austria. Ascheme to divert water from Arzino Riverto the city of Pordenone included a tunnel,5.7 km long, 4.5 m diameter, with a slopeinclination of 1.5% to 2%, mostly throughstable limestone and marl strata. The olderformations overthrust the younger strata,and the tunnel crosses the main fault zone.The area is highly seismic, and, in 1976, amajor earthquake with epicentre near theVal d’Arzino was apparently linked to thefaults crossed by the tunnel. The rockencountered along the tunnel alignmentdemonstrated a large variation in stability.

A large section of the tunnel (63%) wasdriven through good, fair or fairly unstablerock (Class Fl to F3), but the remainder wasthrough difficult, unstable ground (Class F4to F6). The weak formations include rockssuch as marl, mudstone and claystone, withfaults, overthrusts, and weathered rock closeto the surface or affected by undergroundwater. The challenge was to select amachine with high productivity in goodrock, but which would still be able to over-come difficulties in weak and unstable rock.

The contractor, Ilbau, used a brand newRobbins TBM, with Swellex rockbolts assupport. Average advance rate was20.9 m/day and 453 m/month, and highestadvance rate was 90 m/day and808 m/month. TBM utilization varied froma maximum of 45% in Class Fl to a mini-mum of 8.5% in Class F6, averaging25.6%. The penetration rate was between5.5 m/h in Class Fl and 3.5 in Class F5.Rock reinforcement took 44.4% of thetotal time. The contractor worked 2shifts/day, 11 hours/shift.

Best performance was 54 m/day inClass Fl, but a significant achievement was7.4 m/day in Class F6, where heavy rockreinforcement was required, and only 2 mto 4 m/day would be expected. It is inter-esting to note that the good overall perfor-mance was achieved in spite of two poormonths of around 50 m/month.

A delay was caused by an unexpectedmethane gas inflow emanating from ablack marl formation, which accumulatedclose to the machine and caused an explo-sion. Luckily nobody was injured, but tun-nelling stopped for three weeks to upgradegas detection, install safety devices, andimprove ventilation systems.



Effect of rock conditions on the 4.5 m TBM at Val d’Arzino.

Rock class distribution at Alassio.

Project: Water diversion tunnel.Location: Arzino River, Pordenone, Italy.Excavation method: Robbins 4.5 m-diameter TBM.Contractor: Ilbau, Austria.Rock: Limestone and marl, interspersed with mudstone,claystone and weathered formations.Rock reinforcement required: Rapid support behind TBM invariable strata.Rockbolt selected: Swellex.

RR3/RC7.qxd 23/6/05 11:13 Page 89

Alto Adige Treatment Plant

The Alto Adige area of the Italian Alps is aparadise of mountains, valleys and rivers,where protection of the environment is ofparamount importance, especially as thelocal economy relies heavily on tourism.This was uppermost in the minds of plan-ners when a sewage treatment plantbecame an urgent necessity in the MediaPusteria valley, near the Austrian border.Rather than upset the environmentalists,they opted to place the 25,000 sq m plantunderground. This plant is the first of itskind in central Europe, and will serve95,000 people, cleaning 95% of phospho-rus, nitrogen and other oxygen-depletingpollution out of the waste water. The plantwill occupy the smallest possible surfacearea at the bottom of the valley, eliminat-ing odour and noise, and will also be saferin the event of earthquakes. The designand size are in accordance with the latestEuropean regulations, and will achievestrict purification limits.

Alto Adige was a pilot project for Italyas a whole, with a view to building otherfacilities such as reservoirs, storage depots,car parks and sport and recreational facili-ties underground.

The plant consists of a 950 m-long, 3.9 m-diameter headrace tunnel, whichconveys the sewage into large cavernswhere screening, desanding, degreasing,preliminary sedimentation, biological andchemical treatment, are carried out.

Some of the resulting sludge is pro-cessed for agricultural applications, andsome is converted into biological gas tofeed a built-in heating plant, achieving a50% saving in energy costs.

The headrace tunnel and 326 m-longpilot tunnel for the central cavern weredriven by an Atlas Copco Jarva Mk12TBM. Standard Swellex bolts were used for reinforcement in the pilot tunnel,and more than 4,000 Super Swellex in 3 m and 4.5 m lengths were used forreinforcement of the central and sidecaverns.

Blasthole drilling was carried out by anAtlas Copco Boomer H 188 two-boom rig,equipped with service platform. In thedrilling and bolting operations, AtlasCopco Secoroc rock tools were usedthroughout, drilling 51 mm and 64 mmholes. Bolting, using both Super Swellexand cable bolts, was carried out with anAtlas Copco rig equipped with a BUT 35boom and automatic rod adding system. Aservice contract provided for regularmaintenance of the COP rockdrills, which were dispatched to the Atlas Copco workshop in Milan after every5,000 drillmetres.

Above ground, an Atlas Copco ROC612HC with folding boom was used forbenching on the construction site wherethe administration and service buildingswere erected.

The site manager found it a great bene-fit to have a single supplier covering thejob, for drillrigs, rock drilling tools, androck reinforcement. In addition, wheredrilling long holes for bolting in a narrowspace is normally difficult, the rod adding system on the BUT 35 boom madeit easy.

The geologist found that the Swellexbolts fulfilled their safety functionexcellently in the schist rock. They were fast to install and gave immediate rocksupport. ■



Project: Underground sewage treatment plant and tunnels.Location: Media Pusteria valley, Alto Adige, Italy.Excavation methods: 3.9 m-diameter TBM, drill/blast.Contractor: Ilbau srl.Rock: Alpine schist.Rock reinforcement required: 3 m and 4.5 m bolts for pilottunnel and cavern support.Rockbolts selected: Standard Swellex, Super Swellex.

TBM usage statistics for different rock types.

Relation between Classification, ROP and TBM Utilization

Rock ROP Utilization Daily Thrust Cutter load Torque

(m/h) % average (bar) (t/cutter) (amps)

(m/day)

J1 4.61 35.2 35.7 99.5 14.3 125

J2 5.88 38.0 49.2 82.7 11.9 138

J3 3.96 47.1 41.0 93.1 13.4 137

T1 4.71 46.6 48.3 86.9 12.5 133

R 7.70 25.6 43.3 73.7 10.6 144

LT 5.27 19.9 23.1 56.1 8.1 114

F 5.22 21.4 24.5 62.4 9.0 130

CF 5.28 38.4 44.6 76.2 10.9 128

J1 to LT are volcanic rocks-pyroclastites.

F and CF are Brixen quartz-phyllites.

RR3/RC7.qxd 23/6/05 11:13 Page 90

Removing the Bottleneck atSan RoqueUS contractor Raytheon Ebasco OverseasLtd. (REOL) was responsible for the SanRoque dam project on the River Agno inthe Cordillera Mountains of Pangasinanprovince, about 250 km north of Manila,the Philippines capital. The 1,100 m-long,188 m-high dam embankment is believedto be the biggest in Asia, and is the twelfthlargest in the world. It will create a vast 14 sq km reservoir for recreation, providedownstream irrigation to 87 sq km of farm-land, and supply power to the national gridfrom the dam’s integral 345MW hydro-electric power station.

Three diversion tunnels were designed toaccommodate a flood flow of 4,600 cu m/sec.The two largest high-level tunnels are 16.5 m-high, 11 m-wide and horseshoe-shaped. They will each cater to flows up to2,100 cu m/sec. The remaining 400 cu m/secof flood water will go through the smallestlow-level tunnel, which is 817 m-long, 6 mx 6 m, and also horseshoe-shaped. It willnormally have a flow of about 120 cu m/sec.

The underground fleet at San Roquecomprised 22 Atlas Copco WagnerScooptram loaders and Mine Trucks, the

first such equipment to be used in thePhilippines. Six ST-7.5Z loaders workedon the main tunnels, matched by the samenumber of MT-436B mine trucks. Thesewere supported by a further ten of thesmaller Wagner ST-2D units for use in thedam’s grout gallery tunnels. When the sizeof the tunnels was increased, six of theWagner ST-2D loaders were replaced withthe larger Wagner ST-3.5 units.

Exceptional availability of between92% and 96% was achieved, exceeding the85% guaranteed by Atlas Copco. AtlasCopco Wagner’s comprehensive preventa-tive maintenance programme, combinedwith operative training, which is part of thecompany’s on-site full service package,was the key to the equipment’s success.

WORLDWIDE HYDRO


Three diversion tunnel portals at SanRoque.

Swellex in Large HydroelectricProjectsConstruction ReliabilityInternational consultants are increas-ingly specifying Swellex in theirdesigns for hydro projects, becauseof the need for absolute controllabil-ity of installation. Unlike railway andhighway tunnels, hydro tunnels arenot easy to inspect, so there has tobe a greater emphasis on reliabilityof construction methods and materi-als. The fact that projects can bedesigned in one country for construc-tion in another, using materials froma variety of sources, can be a causeof great concern to both the hydrotunnel designer and his client. UsingSwellex as the specified supportsystem reassures both parties thatthe quality, flexibility and reliabilityfactors are fully covered.

Project: San Roque on Agno River, 345 MW.Location: Philippines.Excavation method: Drill/blast. Contractor: Raytheon Ebasco Overseas Limited.Designer: Golder Associates.Rock: Mainly volcanic tuff. Rock reinforcement requirement: Quality control, capacity towork in soft and weak rock. Rockbolt selected: Super Swellex.

RR3/RC8 23/6/05 11:16 Page 91

Super Swellex was specified by thedesigner, Golder Associates of Georgia,US, as the regular pattern bolt. Thishydraulically-expanded bolt gives immedi-ate rock support and full column bond, andhas an excellent quality control procedureduring its installation. An average advance

of 7 m/day was achieved on each face,generally from two 4 m rounds. Afterdrilling, blasting and mucking out, theexposed rock was sprayed with 50-75 mmof fibre-reinforced shotcrete before instal-lation of the 4 m-long Super Swellex bolts.A second application of shotcrete was thenapplied to produce a smooth 350 mm-thicktunnel lining.

Immediate rock support was especiallyimportant when facing the soft and un-stable rock at San Roque. Moreover, insuch rock conditions, reinforcement is abottleneck in the excavation cycle, so thecontractor was pleased with the oppor-tunity to use a fast and trouble-free boltlike Swellex to speed up production.

The 11 m-wide, 8 m-high benchesremaining in the two large tunnels wereduly excavated on schedule before the startof the typhoon season. The Atlas CopcoWagner fleet then moved on to muck outtwo 1,500 m-long tunnels at the site, a 7 m-diameter irrigation tunnel and a 9 m-diameter tunnel to the main powerhouse.

San Roque Power Corporation will selland supply electricity to the national gridfrom 2002 for 25 years, before transferringownership to the Philippines NationalPower Corporation.

WORLDWIDE HYDRO


Economical Support Solutionat UriThe Uri project is located in the foothillsof the Himalayas, in the Kashmir Valley ofnorthern India. The new hydropower plant

will harness the flow of the Jhelum river,and its 480 MW turbines will supplymuch-needed electricity to the region.

Urico contractors, a design/constructjoint venture led by Skanska and NCC,employed six Atlas Copco Boomer H178drillrigs on the development of 22 km oftunnels at Uri. The Boomer H178, with itsthree booms, was selected as the most flex-ible machine available to excavate faces ofcross-sections between 25 and 100 sq m,together with the 22 m-wide machine hallcavern. Average progress in the tunnelswas 250 m/week, with a best week of 278 m. Atlas Copco assisted the contrac-tors with an extensive training programmeto teach the local employees how tooperate the rigs.

Rock reinforcement at Uri consisted ofshotcreting and bolting, with Swellex com-prising 75% of the bolts used. The drillrigswere used for all rockbolting work,installing 700 x 3 m-long bolts/week.Swellex was chosen wherever possible,because they are quicker to install, andmore economical overall, than grouted

Installing Super Swellex at San Roque.

Atlas Copco Boomer H178 face drillingat Uri hydro scheme.

RR3/RC8 23/6/05 11:16 Page 92

rebar bolts. Indeed, in places where waterwas flowing, Swellex was the only realisticoption. The rock encountered varied fromquartz schist to shale, with some of morerecent volcanic origin.

Construction at Uri involved the exca-vation of 1.2 million cu m of rock under-ground, and the placement of 375,000 cu mof concrete lining along the 15 km of watertunnels.

WORLDWIDE HYDRO


Project: Uri hydroelectric power station. Location: Northern India, Jammu and Kashmir. Excavation method: Drill/blast, top heading and bench.Contractor: Joint venture Skanska and NCC.Designer: Skanska/NCC.Rock: Variable, from weak to hard rock. Rock reinforcement requirement: To cut bottleneck inproduction cycle.Rockbolt selected: Standard Swellex.

Right Combination at AltoLindosoAtlas Copco was the main supplier toItalian contractor Torno for the AltoLindoso 600 MW underground hydroelec-tric plant located in northern Portugal,close to the border with Spain. The com-pany provided all of the drilling equipmentneeded for 12 km of headrace, tailrace andaccess tunnels. The power generating plantwas installed in a chamber 70 m south of a110 m-high arched dam with a span of 296 m near the confluence of the CastroLaboreiro and Lima rivers, which providesa maximum head of 338 m.

Atlas Copco helped train the drillrigoperators and maintenance personnel, andprovided a manned workshop container forhydraulic service operations at site.

The five Boomer rigs employed drilledmainly in hard granite with a compressivestrength of between 1,800 and 2,000 bar.Around the tailrace tunnel exits, the

drillers faced weathered granite, as well assome schists and shales.

Torno operated a two-shift system of 12 h/shift, gaining advances of 3.5 m/round.Swellex rockbolts were used exclusivelyfor rock reinforcement, complementedwhere necessary by shotcreting, wire meshand steel arches. The combination of Tornoskills with Atlas Copco service succeededin completion of what had previously beena very troublesome project, and AltoLindoso is now contributing power to thePortuguese national grid.

Project: Alto Lindoso hydropower.Location: Northern Portugal, close to Spanish border.Excavation method: Drill/blast.Contractor: Torno Construction.Client: EDP – Portugal National Power Board.Rock: Hard granite, weathered granite, schists, and shales.Rock reinforcement requirement: To provide temporarysupport for access ramps, tunnel and chambers.Rockbolt selected: Standard Swellex.

View of dam site at Alto Lindoso.

RR3/RC8 23/6/05 11:16 Page 93

WORLDWIDE HYDRO


Super Bolts on the DanubeThe River Danube drives turbines in noless than nine power stations as it wendsits way through Austria. The oldest, atYbbs-Persenbeug, was built in 1959 with

six turbines installed. By the early 1990s,more capacity was required, and it wasdecided to install an additional 48 MWturbine.

The project involved the excavation of a180 m-long x 40 m-deep x 20 m-wideopen pit alongside the existing station,without interrupting its operation. Trialswith drill/blast indicated an unacceptablehigh level of vibration which, combinedwith faulting in the bedrock in the vicinityof the station, threatened the existing tur-bine installations.

It was decided to use hydraulic breakersand excavators, together with additionalrock reinforcement of the vertical walls ofthe pit. The design consultants advised theclient that cement-grouted rockbolts,which take up to a week to set, wouldcause excessive delays to the project.Accordingly, it was decided to use AtlasCopco Super Swellex bolts which, even inthe long lengths required in this unusualinstallation, take only 15-20 minutes toinstall, including the time spent drilling.

Bolts of lengths 8 m, 10 m, and 12 mwere guided into the 48 mm-diameter drill-holes by hand, and then pushed home by oneof the two Atlas Copco drillrigs employed atsite. Some 2,000 Super Swellex bolts wereused, 900 of which were 12 m-long.

The bolts gave instant support to thewalls of the pit, helping keep the project ontime and within budget. The chief engineerof the joint venture constructing the powerstation observed that it would have beenimpossible to stick to the construction sched-ule without the rapid and secure installationoffered by the Swellex bolting system.

Project: 40 m-deep open pit at Ybbs-Persenbeug power station.Location: River Danube, Austria.Excavation method: Hydraulic breakers and excavators.Contractor: JV of Mayreder-Kraus, Porr, Universale, HofmannMaculan, Stuag, Ilbau, Strabag.Rock: Faulted bedrock.Rock reinforcement required: To secure vertical faces of openpit.Rockbolt selected: Super Swellex up to 12 m-long.

General view of open pit at Ybbs-Persenbeug power station.

Inserting 12 m-long Swellex rockboltto support the cut beside the Danube.

RR3/RC8 23/6/05 11:16 Page 94

Rock Mass Stabilization atTala HydroTala Hydro scheme has been constructedin the remote Himalayan kingdom ofBhutan, using more than 40 items of capi-tal equipment supplied by Atlas Copco.The dam site is about 85 km by road fromthe border with India, and is located nearthe village of Wangkha, on the Wangchuriver, some 3km downstream of the exist-ing Chukha tailrace outfall.

Hindustan Construction found MAIanchors were crucial for stabilization ofthe walls of the desilting chambers at Tala,and as primary support during excavationof the Head Race Tunnel (HRT). The sameanchors have also been found to be veryuseful in reducing pore water pressurebehind the support system.

Major features of Tala are: three desiltingchambers sized at 250 m x 13.9 m x 18.5 m;a 22.97 km-long, 6.8 m finished diameter,50 sq m modified horseshoeshaped, con-crete-lined headrace tunnel (HRT); and anunderground powerhouse 206 m-long by 19m-wide and 45.5 mhigh, with transformercavern 191 m-long by 16 m-wide and 27 m-high. The HRT, which has been excavatedat 7.5 m-diameter with rock cover of 60 mto 1 km, utilized five construction adits. Inthe tunnels, Atlas Copco Boomer 352s wereused in rock classes 1, 2 and 3, where theaverage advance was 120 m/month, and inclass 4 rock up to 70 m/month. Class 5rock, which had to be fully ribbed at 60-75cm intervals, strutted, bolted, meshed andshotcreted, slowed advances to 30 m/month.The Atlas Copco Secoroc button bits werereported by the contractors to have

achieved up to 30% longer life thanexpected.

Hindustan Construction used MAI selfdrilling anchors (SDA) for stabilizing thereinforced concrete wall of desiltingChamber No 3. The wall of the chamberwas anchored to the deeper competent rockusing one row of 114 MAI SDA with 20 mlength and 38 mm-diameter at 3 m centres,and another row of 36 MAI SDA with 24m length and 51 mm-diameter at 3 m cen-tres. 32 t pull out tests conducted on the 38mm-diameter and 20 m-long MAI SDAresulted in displacements of 11 mm and 17mm respectively, well within specification.

Hindustan Construction used theDrainage, Reinforcement, Excavation,Support Solution (DRESS) in the 330m-long section of HRT affected by adversegeology in Package C4. Here, MAI SDAswere used both as radial bolts and asdrainage elements, in combination withOdex Piperoofs. For anchoring steel arches,SDA of 8-12 m lengths were installed in asystematic pattern. If no water seepageresulted, they were grouted. Two 38 t pullout tests were conducted on 38 mm-diame-ter, 8 m-long MAI anchors to check theefficacy of grouted anchors in the poorstrata in the HRT. These passed, with dis-placements of 16 mm and 22.8 mm.■

WORLDWIDE HYDRO


Project: Tala Hydro on Wangchu river, 1,020 MW.Client: Tala Hydro Power Authority (THPA).Location: Wangka, Kingdom of Bhutan.Excavation method: Drill/blast.Contractors: Jaiprakash; Hindustan Construction; Larsen &Toubro.Rock: Gneiss with quartzite bands and biotite schists.Rock reinforcement requirement: Roof support.Rockbolt selected: MAI SDA.

Atlas Copco Boltec 435H at work inTala headrace tunnel.S.D. Jeur, Project manager, Hindustan Construction

Company, C4 Package used Atlas Copco Odex forpiperoofing, in combination with MAI SDAs, to maketunnelling possible through soil.

RR3/RC8 23/6/05 11:16 Page 95

RR3/96 24/6/05 15:38 Page 1

Bullet Train Secured onKyushuDaini Shibisan is a twin-track railwaytunnel, part of the high-speed railway systemunder construction between Kagoshima andKumamoto on the large island of Kyushu,south of the Japanese mainland.

The 3,394 m-long tunnel, one of thir-teen in the section, was excavated by theKajima-Zenitaka-Shita joint venture, whohad to overcome major problems with theamount of groundwater present in thesandstone, shale and clay strata.

Drilling and reinforcement was compli-cated, with some holes collapsing as soonas they were drilled, making it virtuallyimpossible to inject the cement required togrout rockbolts. The solution was AtlasCopco Swellex rockbolts, which expand tofill the hole, need no cement, and have theadvantage of providing immediate rein-forcement to the surrounding rock. AtlasCopco Boomer drifting rigs installed thebolts, which were expanded using an ESP-A51 electric Swellex pump.

In this type of environment, Swellexbolts are known to perform much betterthan conventional bolts, and are also morecost-effective. Their introduction intoDaini Shibisan tunnel ended the expensive

business of having to re-excavate rockwhen it had been deformed by less-effective reinforcement methods.

The site manager described the Swellexcontribution to the operation as highlyvaluable, and an extremely efficient andreliable method of dealing with the porousand highly-fractured rock formation.

MAINLAND JAPAN


Portal at the Daini Shibisan high speedrailway tunnel.

Installing Swellex rockbolts at theDaini Shibisan face.

Top Combinations in JapanSpeed with SafetyTunnelling operations in Japan are tothe highest standards of quality andsafety, and Swellex was originallyintroduced as a problem solver in spe-cific rock conditions such as highwater inflow and squeezing ground.Since then, Swellex has been used toreplace steel arches on a number ofprojects, to good effect. Experienceobtained on the more difficult projectshas led to Swellex being specified as apattern bolt in current projects,mainly where grouted rebars are con-sidered too slow to install and takeload. Wherever there is rapid defor-mation of the strata, Swellex is thebolt of first choice because of its fastinstallation and immediate load bear-ing characteristics. In Japan, it is apopular combination of speed withsafety, controllability and reliability.

Project: High Speed Railway, Daini Shibishan.Location: Kyushu Island, Southern Japan.Excavation method: Drill/blast.Contractor: Kajima-Zenitaka-Shita joint venture.Project Owner: JR – Japan Railways. Rock: Weak formation of shale, sandstone and clay strata.Rock reinforcement requirement: Versatility to cope withgeology, immediate rock support, non sensitive to water inflow.Rockbolts selected: Super Swellex, Midi Swellex.

RR3/RC9.qxd 23/6/05 11:19 Page 97

Solving a Geological Puzzlewith Swellex

At the 3,692 m-long Sobu tunnel located inmountainous terrain on the road betweenKyoto and Yonago Tottori prefecture, topperformance was achieved by COP 1838rock drills fitted to a Rocket Boomer H195. The cross-section at Sobu is between90 and 100 sq m, and excavation was bymicro-benching, a common method inJapan.

The rock is sandstone, shale, tuff andporphyrite, with a compressive strength of 400-500 bar. The drillrig achieved 100holes in 40-50 minutes, with a penetrationrate of 3 m/min, and total advance was 6 m/day.

Site management reported low con-sumption of shank adapters and otheraccessories.

Japanese tunnels require the higheststandards in safety and support, and thequality of rockbolts, and their standard ofinstallation, are paramount.

Initially, in Japan, Swellex bolts wereemployed as a problem solver for specificrock conditions, such as squeezing groundand high water inflow. They have alsobeen used in difficult situations to replacesteel arches. Lately, large quantities of

Swellex bolts have been employed in pat-tern bolting on a number of projects inheavy and fast deforming ground, wheregrouted rebars are considered too slow totake load. There is also increasing accep-tance of Atlas Copco MAI SDA selfdrilling rockbolts. ■

Easily Through Difficulties onHonshuThe Chuo Highway connects Tokyo andNagoya in central Japan, and work is underway to widen the road from two to threelanes. Shin-Iwatono is one of the tunnelsexcavated along the alignment, and islocated 100 km north west of the capital.Work on the 1,591 m-long tunnel, with itscross-section of 130 sq m, was carried outby the Tobishima/Aisawa joint venture forJapan’s Public Highway Corporation.

Rock at the site is andesite lava and tuff-breccia. The first 126 m of tunnel excavationwas by roadheader in soft tuff-breccia. Drill-and-blast operations then commenced inandesite lava using an Atlas Copco RocketBoomer 352-2B, the first in Japan, andleased by local distributor Drill Machine.

The Rocket Boomer 352-2B is equippedwith two BUT 35 booms, with COP 1838rock drills mounted on BMH 6812 feeds. Ad-vance per round was 1.2 m, with penetration

rates of 2.5 m/min in the tuff-brecchia, and3.0 m/min in the harder andesite.

Swellex rockbolts were selected becauseof their versatility and effectiveness in thevarying ground conditions, and the speedwith which they could be installed. Theseproperties were particularly important in thesofter strata mined by the roadheader.

MAINLAND JAPAN


Project: Chou Highway,Shin-Iwatono tunnel.Location: HonshuIsland, Central Japan.Designers: JH, JapanHighways. Excavation method:

Roadheader, drill/blast.Contractor:

Tobishima/Aisawajoint venture.Rock: Variablevolcanic formationincluding andesite,tuff and breccias.Rock reinforcement

requirement: Safety,versatility to cope withgeology, even in softlayers.Rockbolt selected:

Super Swellex, MidiSwellex.

Project: Sobu roadtunnel.Location: HonshuIsland, Central Japan.Excavation method:

Drill/blast,microbenching.Rock: Mixture ofsedimentary andvolcanic rockformations.Rock reinforcement

requirement: Safety,versatility to cope withgeology, even in softlayers.Rockbolt selected:

Super Swellex, MidiSwellex.

Rocket Boomer 352-2B rockbolting at Shin-Iwatonohighway tunnel.

Rocket Boomer H 195 micro-benching at Sobu roadtunnel.

RR3/RC9.qxd 23/6/05 11:19 Page 98

Umbrella System atMontegiglio

Montegiglio tunnel, in Italy, is a 9.36 km-long, 4.5 m-diameter connection intendedto support the mineral extraction activityof Colle Pedrino and Montegiglio quarries.A conveyor belt for the movement of min-eral to the Calusco d’Adda cement plant isinstalled in the tunnel.

From the south entrance of Montegiglioquarry, a cableway to Pontida valley linksthe two quarries. The tunnel was driven byTBM on a different alignment, westwardand more northerly. For the first 800 m, thetunnel proceeded straight on a SW-NEheading beneath Carvico village at adownward slope of 11.4%. The TBM was

SDA WORLDWIDE


Umbrella of 24 MAI SDA type R51L atMontegiglio.

Front Stabilization Using MAIAnchorsImproving RockQualityDrilling ahead of the tunnel face and

installing bolts or grout is a com-

mon way of improving rock quality

before actual excavation takes place.

Atlas Copco has, as a supplier,

been involved in a number of such

projects, both in mining and

construction.

Pre-reinforcement is a different

way of approaching ground control.

Instead of relying on supporting the

ground following excavation, pre-

reinforcement increases rock

strength prior to excavation. There

are several benefits to this. First, a

pre-reinforced rock mass will be less

damaged by blasting, and less dis-

turbed by elastic and non-elastic

stress redistribution around the exca-

vation. Second, the rock mass is

never without support, even at the

split second following blasting of the

round. Third, the support can be

more active when installed early,

rather than passive when installed

later. Fourth, pre-reinforced ground

will not deteriorate or collapse as

rapidly as a totally unsupported exca-

vation, allowing a safe working

period for installation of regular

support.

In tunnelling, the umbrella grout-

ing method of pre-reinforcement is

frequently used. This method pre-

supports the planned roof area with

steel rods. Large holes are drilled in

the future roof perimeter, and grout-

ed at high pressure with high

strength, fine grained cement grout.

Through each cemented hole, a

smaller hole is then drilled, in which

a high-strength reinforcement bar is

grouted. Although highly effective for

shallow tunnels driven in very

adverse ground conditions, it is easy

to see that such a work-intensive

operation would be deemed neither

practical nor economic for mining

applications, although the underlying

concept could definitely be useful.

Project: Mineral conveyor tunnel 9.36 km-long with 4.5 m-diameter.Location: Pontida Valley, Italy.Excavation method: Open gripper TBM.Contractor: Strabag Del Favero.Rock: Flysch and micaceous sandstones with silts and claylayers.Rock reinforcement required: Umbrella of 24 x 9 m-long bolts.Rockbolt selected: Atlas Copco MAI Self Drilling Anchors.

RR3/RC10.qxd 23/6/05 11:20 Page 99

SDA WORLDWIDE


operated 5 days/week in three 8 hshifts/day, with maintenance carried outduring the morning shift.

Every 200 m of advance, the TBM had tobe stopped for a shift to extend the conveyorbelt. The conveyor belt storage was locatedin the area in front of the south entrance.

The stabilization and support interven-tions for the Montegiglio tunnel dependedupon the observed geological and geotech-nical conditions of the rock. Six types weredefined, ranging from non-systematicintervention, to bolts with increasing thick-ness of shotcrete, up to bolts with net, ribsand reinforced shotcrete.

During the initial excavation in theFlysch di Bergamo geology, contractorStrabag Del Favero suspected weak groundconditions ahead, and performed a horizontal

investigation along the axis of the tunnel.The results showed that further advancewith the TBM would achieve only limitedresults. In fact, at that point, the excavationmet micaceous sandstones, with silts andclay layers with the consistency of dampsand. These exhibited very low cohesion,or no cohesion at all, due to the weak grainbond. In these conditions, excavationbecame difficult, with some collapse ofmaterial from the crown. The supportdesign for this particular type of sectionspecified an umbrella of steel pipes withdiameter 104 mm, with a length of 12 m and 3 m overlap. Due to the smalltunnel diameter of 4.5 m, only limitedspace was available for positioning andworking the drilling equipment, so analternative solution was needed.

Atlas Copco proposed the use of aBoomer H145 equipped with two boomsand COP 1440 rock drills. The feed lengthwas adapted to 4.4 m to suit the tunneldiameter, to enable Strabag Del Favero toinstall radial anchors. More importantly, anumbrella could be installed consisting of24 Atlas Copco MAI SDA of type R51L,with a length of 9 m and a overlap of 3 m.This allowed the contractor to excavate atotal of 6 m, in steps of 1 m, before placingthe next umbrella.

After some initial mechanical adjust-ments on the Boomer, it was found that theumbrella could be installed within a periodof 15 h, facilitating faster excavation of thetunnel.

Presupport at Pakuashan

The 5 km-long Pakuashan tunnel is beingconstructed over a seven-year period inCentral Taiwan, as part of the Hanbau-Tsaotwen Expressway, one of 12 plannedeast-west connections. NATM is beingused, despite the poor geological condi-tions, which do not fit any of the com-monly used rock classifications.

The Pakuashan ridge is an anticlinalstructure of rocks, which may be subdividedinto two main geological groups. Firstly,1 m-thick alternations of mudstone orclay of hard to very hard consistencyand low degree of cementation, and sand-stone, appearing as loose to medium densesand. Secondly, silty-sandy gravel withcobbles and occasional boulders of maxi-mum diameter 50 cm. The matrix isfrequently slightly weathered, and cemen-tation generally poor. Groundwater is a keyfactor governing rock mass behaviour.

Twin tubes with 120 sq m section arebeing excavated from all four portals, inloose to heavily compacted gravels. The 65 sq m top headings are maintained 60-70 m ahead of the benches, and invertclosure follows 6-10 m behind each bench.20 m-long x 4 in-diameter drainage holes

Project: Twin-tube 5 km-long highway tunnel.Location: Hanbau-Tsaotwen Expressway, Taiwan.Excavation method: NATM with top heading, bench and invert.Consultant: China Engineering Consultants Inc.Rock: Gravel with mudstone and clay alternations.Rock reinforcement required: Presupport around arch andsidewalls, roof support.Rockbolt selected: Atlas Copco cement grouted SDA.

BSH 110-SDA for handling MAIanchor.

RR3/RC10.qxd 23/6/05 11:20 Page 100

SDA WORLDWIDE


are drilled ahead of the face, using casing.Excavation is by backhoe, with a ripper forprofiling.

Presupport consists of 3 m-long fore-poling using SDA around the arch andsidewalls at 0.5 m spacing. Lattice archesare then set at 1 m centres, and 4 m and 6 m SDA cement grouted rockboltsinstalled, along with two layers of wiremesh and 300 mm of shotcrete. A layer ofwire mesh and 200 mm of shotcrete arelaid on the floor of the top heading astemporary support.

This is the first use of SDA in Taiwan.One in 50 of the installed bolts is subjectedto a 17.6 t pullout test.

Maximum advance on a top heading hasbeen 3.3 m/day of 24 h, and the site works7 days/week. Around 800 m from the por-tals, the faces moved from compactedgravel into sand with very little cohesion,slowing advance rates considerably.

Effectiveness of the support regime ismeasured using arrays of convergencebolts installed at 20 m intervals. There isalso a cross section of extensometers at200 m intervals which measure at depthsof 3 m, 6 m, and 9 m into the profile rock.Every 500 m, radial pressure cells andstrain gauges are installed in the shotcrete,together with measuring anchors to recordstress and strain in the ground. Resultsfrom all three sets of stations are analyzedand compared to theoretical behaviour.

In addition to the main tunnels, there are nine pedestrian cross passages, threevehicle cross passages, and ten emergencyparking bays. A 240 m-deep x 10 m-diam-eter ventilation shaft has been constructed

in the centre of the alignment using NATMtechniques, allowing four more faces to beopened, and facilitating dewatering.

A 400 mm-thick cast concrete liningwith waterproofing membrane and drainagesystem will be installed as final support.

The mechanical behaviour and engi-neering characteristics of the gravel forma-tion are related to the degree ofcementation of the matrix and the percent-age gravel content.

Based on the monitoring data, maximumcrown settlements of about 400 mm havebeen observed in areas of fine sedimentswith ground water, while in sections withdense gravel, 50 mm is typical. Maximumshotcrete stresses of 150-200 kg/sq cmhave been measured, within the designshotcrete strength of 210 kg/sq cm.

Reinforcing Feuerletten Clay

In Autumn 1998, work started on a newhigh speed railway line between the citiesof Nuremberg and Ingolstadt, forming thenorthern part of the proposed high speedconnection between the two majorBavarian cities, Munich and Nuremberg.

The Göggelsbuch tunnel, which has atotal length of 2,287 m and an excavatedcross-section of 150 sq m, is the only nat-ural tunnel in the north section of thisalignment. It is equipped with an emer-gency shaft that is connected to the surfaceby two 150 m-long galleries.

Although smaller than the two 7 km-long tunnelling projects in the middle

section of the railway, the Göggelsbuch isunique, as its alignment runs through alayer of Feuerletten, a hard, solid claywhich is subject to shrinkage crackingwhen dry. Once in contact with water,Feuerletten softens and becomes imperme-able due to a swelling of its clay minerals.

Project: Nuremberg-Ingolstadt high speed railway.Location: Ingolstadt, Germany.Excavation method: Mechanical excavator.Contractor: Bilfinger Berger and Max Bögl joint venture.Rock: Hard, solid Feuerletten clay.Rock reinforcement requirement: Forward face support,systematic roof support.Rockbolts selected: Atlas Copco MAI SDA, SN anchors.

Installing 6 m-long SDA at Pakuashan.

RR3/RC10.qxd 23/6/05 11:20 Page 101

SDA WORLDWIDE


The 35 km-long northern section of therailway line, including the Göggelsbuchtunnel, is under construction by a jointventure of Bilfinger Berger and Max Bögl.

It has a reinforced concrete lining vary-ing between 75 and 125 cm in thickness atthe invert, and which is a constant 35 cm-thick in the arch. A single 3 mm layer ofpolyethylene membrane helps to seal thetunnel lining against a water head of 30 m.

The anchorage systems used in the con-struction of the tunnel comprised 4 m-longSN anchors and Hollow Bolt Type MAIanchors with varying lengths. DywidagSystems International (DSI) supplied bothsystems. The DSI hollow bolt anchor typeMAI is optimally used wherever geologi-cal conditions would normally requirecased drilling to place anchoring or nailingelements. Its advantage lies in the simplic-ity of the system, the flexibility in its

length achieved by coupling sectionstogether, and the quick and economicalinstallation method.

Swelling Clay

The Göggelsbuch tunnel runs exclusivelyin the Feuerletten layer, with between 4and 20 m of Feuerletten overhead. Theclay comprises a clay stone with fine tomedium sand, which is locally interruptedby up to 5 m-thick sequences of pure sand-stone, and by up to 10 m-thick sequenceswith alternating sandstone and clay stone.The layers of Feuerletten are usuallyorientated horizontally.

The swelling of the clay, and the pres-sure exerted, have been examined and ana-lyzed precisely. All the tests demonstratedthat the pressure due to swelling, in con-nection with the hydrostatic load, was notdecisive in calculating the internal lining.

Groundwater-filled layers of sandstone,and impermeable layers of clay withgroundwater flowing on them, were pre-sent during the complete advance works.After the whole tunnel had been excavated,an underground water flow of 5 l/s wasmeasured.

Construction was from May, 1999 untilSeptember, 2000, advancing simultaneous-ly from both north and south portals. Thetop heading forming the crown was holedthrough before the bench and invert werestarted.

Concrete lining, from south to north,took some five months from December,2000 with one wagon for the invert form-work, carrying two forms. Two separatelyrunning forms were used for the crownlining, which took another 4-5 months.

Supporting Production

The rock was excavated using a tunnelexcavator along its entire length, with ahydraulic breaker in sections with thicklayers of sandstone. The advance per sec-tion was limited to 1.3 m. The tunnel wassecured with a 20-35 cm-thick layer ofsite-mixed shotcrete, and 4 m-long x 25 mm-diameter SN anchors were installedfor systematic rockbolting.

The crown invert was supported with atemporary shotcrete layer to minimizemovement. Trials without the temporarysupport showed unpredictable results, andthe roof above the crown had to be

Aerial view of Göggelsbuch tunnel.

Supporting the face at Göggelsbuch.

RR3/RC10.qxd 23/6/05 11:20 Page 102

SDA WORLDWIDE


strengthened over a length of 50 m, due toexcessive movement.

While advance from the south pro-gressed with hardly any problems, thenorth drive suffered poor face stability.Despite continuously increasing the dens-ity of support, a face collapse occurred inJuly, 1999. The supports that wereinstalled at that time were: 30 cm of shot-crete in the arch; 20 cm of shotcrete on thearch invert; system anchorage with 4 m-long SN anchors, at 7 units/m; 10 cm ofreinforced shotcrete on the working face; 8 m-long MAI R32 face anchors, at 9 unitsper section; and 6 m-long MAI R32 rods,at 35 units/m.

It was decided to keep the same types ofsupport, but those guaranteeing the stabilityof the working face were intensified. Thelength of the MAI face anchors wasincreased to 12 m, and the number doubledto 18 per round. The length of the MAIR32 steel rods was also increased from 6 m to a maximum 8 m. This intensifiedsystem of face support was installed over alength of 500 m, once the collapsed facehad been cleared. No further collapsesoccurred on the remaining crown drive,which was completed without further delay.

The excavation of the bench and theinvert of the tunnel were subsequentlycompleted in about the half the scheduledtime, catching up on the contract.

Acknowledgements

Thanks are due to Thomas Müller ofBilfinger Berger, and Frank Schmidt ofDSI, for describing the constructionprocess.

Self Drilling Anchors at NorthDowns

The Channel Tunnel Rail Link (CTRL) isthe link between King’s Cross Station inNorth London and the tunnel terminal onthe coast. This link is being built in twophases. The first comprises the 3.2 km-long North Downs tunnel along with threeother major civil engineering contracts,and was begun in 1998/99. The secondphase will comprise four separate contractsand utilize a total of eight TBMs. PhaseTwo started in 2001.

The contract to construct the NorthDowns tunnel was awarded to Eurolink, ajoint venture between Beton undMonierbau of Austria, Miller of the UKand Dumez/GTM of France. The tunnelwas constructed through chalk stratacommon to the region, using NATMtechniques.

The likelihood of poor ground condi-tions is increased at the tunnel portal,where the weaker rock has been exposed toweathering. Also, geotechnical engineeringcalculations show that there are increased

stresses where the tunnel barrel is discon-tinued at the portal.

At the London portal, some form ofadditional ground support was required to allow NATM tunnelling to progress. Itwas decided to drill a total of 24 holes at0.5 m centres around the crown of thetunnel. These were installed 15 m deep at115 mm diameter, using the Atlas CopcoBoodex system. The holes were lined witheasy-to-handle 1.5 m lengths of attachedcasing.

A false portal was built at the entrance,and the spacing of the steel arches wascontinued at 1.5 m as the tunnel advancedunder the crown umbrella. ■

Project: High speed railway tunnel.Location: North Downs, Kent, England.Excavation method: NATM.Contractor: Eurolink jv of Beton & Monierbau, Miller, andDumez/GTM.Rock: Chalk with possible flint bands.Rock reinforcement required: Secure portal area for NATMadvance.Rockbolt selected: Atlas Copco MAI SDA.

Excavating the bench at Göggelsbuch.

RR3/RC10.qxd 23/6/05 11:20 Page 103

KEMI, FINLAND


Introduction

Outokumpu is one of the world’s largeststainless steel producers, accounting forabout 8% of global stainless slab output, anda similar share of cold rolled production.These are hugely significant proportions of amarket that has risen by an average of 5.5%per annum over the last 20 years, and is cur-rently enjoying 7% growth.

Mainstay of the Outokumpu strategy isits highly cost-efficient fully integratedmine-to-mill production chain in the Kemi-Tornio area of northern Finland. An ongoinginvestment programme of EUR1.1 billionwill expand total slab capacity from 1.75million t to 2.75 million t, and coil rollingcapacity from 1.2 million t to 1.9 million t.

Ore reserves at Kemi chrome mine areabundant, and the efficiency of the Torniosmelter is enhanced by its proximity to boththe mine and harbour facilities. Mining pro-duction has been progressively switchedfrom surface to underground, where inten-sive use is being made of information tech-nology to optimize the overall mining andprocessing operation. Underground miningstarted in 2003 at 150,000 t/y, and produc-tion will increase to the planned level of 1.2million t/y by 2007. Open pit mining willcease in 2006.

Reserves

The Kemi deposit is hosted by a 2.4 billionyear old mafic-ultramafic layered intrusionextending for some 15 km north-east of the

Rock Reinforcement at KemiChrome MineIntelligent MiningThe large chromite deposit being

mined by Outokumpu at Kemi,

Finland has a lower than average

Cr2O3 content of about 26%, so

chromite and ferrochrome production

technology has had to be continuous-

ly upgraded to remain competitive.

The Intelligent Mine Implementation

Technology Programme of 14 projects

achieved real time control of mine

production in precise coordination

with the needs of the mineral pro-

cessing plant and the ferrochrome

smelter. The system utilizes a fast,

mine-wide information system that

can help optimize financial results for

the whole operation. Computerized

drilling with Atlas Copco Rocket

Boomers and Simbas, accurate coring

with Craelius rigs, reliable rock rein-

forcement with Cabletec and Boltec

rigs with Swellex bolts and pumps,

and the dependability and longevity

of Secoroc drilling consumables sup-

port this unique mine strategy. The

result is cost-efficient, integrated pro-

duction, on a model which may form

the basis of the next generation of

mining techniques.

Aerial view of Kemi mine, locatedclose to Finland’s border with Sweden.

Kemi underground mine simplifiedlong section.

300

500

550

Crusher

Trial Stoping area

350 Repair shop350 Pump station

475450

275

190 m3/s

115 Repair shopEAR4 FAR2EAR3

450 Expl. storage

500 Pump stationand Repair shop

70 m3/s140 m3/s

Final pit bottom

600

580 Pump station

277

Backfill raise

Backfilling station

Backfill raise

RR3/RC12 19/7/05 10:14 Page 104

KEMI, FINLAND


town itself. The chromite-rich horizonappears 50-200 m above the bottom of theintrusion, and has an average dip of 70degrees northwest. The main immediatehost rock is weak talc-carbonate, in whichthe hanging wall contact is clearly defined.At the footwall, the chromite and host rockare inter-layered, and must be mined selec-tively. However, there is strong granitesome 80 m below the footwall.

The Kemi chrome deposit comprises 11mineralisations within a 4.5 km-long zonevarying from 5-105 m in width, with aver-age thickness of 40 m, a mineral resourceof 150 million t of 28.6% Cr2O3. Of thisthere are 50 million t proven reservesunderground between the 500-m level andthe bottom of the open pit. The ore bodycontinues at depth, probably to 1,000 m,with 750 m having been reached by thedeepest exploratory hole. The 1.5 km-longx 500 m-wide main pit has a final planneddepth of 220 m.

A two shift/day, five day/week pattern isworked in the mine, from which about 1.2million t/y of ore grading 24-26% Cr2O3 isprocessed continuously by the concentrator.The yield is 220,000 t/y of 12-100 mmlumpy concentrate with 35% Cr2O3, and420,000 t/y metallurgical grade concentrateat 45% Cr2O3. Over the years, some 30million t of ore have been produced fromopen pits, resulting in 130 million t inwaste heaps.

Ore Grade Control

Ore grade control in both the open pit andthe underground mine involves intensivewire line diamond core drilling, to deter-mine boundaries and qualities of specificore types. In addition, all blast holes in theopen pit are sampled. Technical innova-tions for ore characterization and quantifi-cation include OMS-logg down holelogging, and automated image analysis forestablishing grain size distribution.

Basic production data about mineralogi-cal and process histories are logged for eachore stope on a daily basis, and this is mergedand compared with daily and blast-specificproduction histories from the database.

Each ore blast is treated selectively atthe concentrator, in order to minimize feedvariation and maximize process stability.

In the concentrator, total chromite recov-ery is around 80%, depending on the pro-portion of lumpy ore. Metallurgical grade

concentrate contains about 45% Cr2O3 of0.2 mm grain size, while upgraded lumpyore is about 35% Cr2O3 with 12-100 mmsize. The former is pelletized at Tornio, andthen mixed with upgraded lumpy ore beforesmelting to produce ferrochrome.

Concentrator operation is optimized byaccurate calibration of the feed slurry ana-lyzers, and control of product quality fromeach unit process, both by compensatingfor changes in feed type, and measuringproduct quality on-line. Manual input canbe used, as well as on-line information.

A Craelius Diamec 264 APC drill rig car-ries out 10 km of coring each year. Drill sec-tions are established every 10 m anddownhole survey is standard procedure, usinga Maxibore system. Based on the drill holedata, a 3D model of the orebody is createdand used as a basis for production planning.

Atlas Copco Simba M6 C at work inthe sublevels at Kemi mine.

Atlas Copco Rocket Boomer L2 C isused for sublevel development.

RR3/RC12 19/7/05 10:14 Page 105

Tying all these streams of collected dataand planning outputs together requires anextremely fast communications network,interfacing with a single master database.

Underground Infrastructure

The main decline starts at a portal in thefootwall side of the pit, at about 100 mbelow the rim. The decline is mostly 8 mwide x 5.5 m high, to accommodate pass-ing vehicles. It descends at 1:7 to a depthof 600 m at the base of the hoisting shaft,and connects with several intermediatesublevels. The decline is asphaltedthroughout most of its length.

There is also a 5,000 cu m repair shopfor open pit equipment at the 115 m level,and a larger 14,000 cu m workshop at the350 m level for the underground mobileequipment fleet. The final 23,000 cu mmain workshop is under construction at the500-m level. The 350-m level workshopsare enclosed by megadoors, which keep inthe heat so that an ambient 18 degrees Ccan be maintained. The service bay is

equipped with a 10 t travelling gantry and16 m-long inspection pit. The washing bayis equipped with two Wallman hydraulical-ly controlled washing cages, so there is noneed for operatives to climb onto themobile equipment.

The main pumping station is located at the350 m level, and has pumping capacity of 2 x250 cu m/h. The slurry-type pumps, withmechanical seals, pump the unsettled minewater to the surface with a total head of 360m. Two other dewatering pumping stationsare located at the 500 m and 580 m levels.

The crusher station at the 560 m level isequipped with a 1,000 t/h Metso gyratorycrusher. This is fed from two sides byvibrating feeders from separate 8 m-diame-ter main ore passes from the 500 m level,and from one side by a plate feeder, towhich the ore can be dumped from the 550m level. A 40 t travelling gantry crane ser-vices the entire crusher house. Crushed oregravitates onto a conveyor in a tunnelbelow the crusher for transport to the shaftloading pockets 500 m away.

Underground Production

Trial stopes in three areas accessed fromthe 275 m and 300 m levels were mined todetermine the parameters of the bench cut-and-fill technique to be used. These had awidth of 15 m, and were 30-40 m-long,with 25,000-30,000 t of ore apiece. Bothuphole and downhole drilling methodswere tested, and 51 mm-diameter down-holes selected as being the safest.

For production purposes, 25 m-hightransverse stopes are laid out, with cablebolt and mesh support to minimize dilu-tion. Primary stopes are 15 m wide, andsecondary stopes 20 m wide. Cementedfill, using cement, furnace slag from aniron ore smelter and fly ash from localpower stations, is placed in the primarystopes, while the secondary stopes will bebackfilled with mine waste rock. The pri-mary stopes are being extracted one or twolevels above the secondary stopes.

Mining sublevels with 5 m x 5 m crosssections are being established at 25 m ver-tical intervals, using one Atlas CopcoRocket Boomer L2 C drillrig equippedwith 1838 ME rock drills and 5 m-longSecoroc steel and bits. Rounds of 60-80holes take about 2 hours to drill, chargeand prime. An emulsion charging truckwith elevating platform and Atlas Copco

KEMI, FINLAND


Atlas Copco Craelius Diamec 264 APCat work underground.

Atlas Copco Boltec LC installingSwellex Mn12 rockbolts.

RR3/RC12 19/7/05 10:14 Page 106

GA15 compressor provides fast and effi-cient explosives delivery. The footwallgranite is very competent, but lots of rockreinforcement is required in the weakerhost rock, where all drives are systemati-cally rock bolted and secured with steelfibre reinforced shotcrete.

The planned nominal capacity is 2.7 mil-lion t/y of ore, which allows for increasedferro-chrome production at Tornio whenOutokumpu decides to expand the smeltingoperation. The total cost for mine develop-ment is EUR70 million.

Rock Reinforcement

Swellex Mn12 2.4 m-long bolts are used forsupport in ore contact formations. These arebeing installed at a rate of 80-120 bolts/shiftusing an Atlas Copco Boltec LC rig, whichis returning drilling penetration rates of 3.2to 4 m/min. The CAN-bus controlled LC rigmounts the latest Swellex HC1 pump, forbolt inflation at 300 bar pressure, andreports progress on the operator’s screen.

The HC1 hydraulic pump is robust,simple, and with low maintenance cost.Coupled to an intelligent system, it reachesthe 300 bar pressure level quickly, andmaintains it for the minimum time for per-fect installation. Combined with the rig’sCAN-bus system, the pump can confirmthe number of bolts successfully installedand warn of any problems with inflation.Over 50,000 bolts have been installed todate without problems.

A series of slip-pull tests carried outthroughout the mine proved the stronganchorage capacity of Swellex Mn12, bothin the orebody and for the softer talc-carbonate and mylonite zone.

Cable Bolting

Kemi installs some 80 km of cable bolt eachyear using its Atlas Copco Cabletec L unit,which is based on the longhole productiondrilling rig Simba M7, with an added secondboom for grouting and cable insertion. TheRig Control System (RCS), enables the oper-ator to pay full attention to grouting andcable insertion, while drilling of the next holeafter collaring is performed automatically,including pulling the rods out of the hole.The main benefit of the two-boom concept isto drastically reduce the entire drilling andbolting cycle time. Also, separating thedrilling and bolting functions prevents the

risk of cement entering the rock drill, therebyreducing service and maintenance costs.

Kemi tested the prototype Cabletec Land eventually purchased the unit afterminor modification proposals. During thetesting period, where most holes were inthe 6 to 11 m range, the rig grouted andinstalled cables at rates of more than 40m/hour. The capacity of the unit, which isgoverned by the rate of drilling, providedaround 50 per cent extra productivity com-pared with alternative support methods.

The Cabletec L is equipped with a COP1838 ME hydraulic rock drill usingreduced impact pressure with the R32 drillstring system for 51 mm hole diameter.The machine’s cable cassette has a capac-ity of 1,700 kg and is easy to refill, thanksto the fold-out cassette arm. It featuresautomatic cement mixing and a silo with acapacity of 1,200 kg of dry cement, whichis mixed according to a pre-programmedformula, resulting in unique quality assur-ance for the grouting process.

Bench Cut and Fill

The current mining method is bench cut andfill, a type of sub-level stoping with down-hole production drilling, in which primarystopes are 25 m high, 15 m wide andbetween 30 and 40 m long. Using a RocketBoomer L2 C rig, the drifts for the primarystopes are developed laterally from thefootwall through the ore zone. Then a SimbaM6 C production rig drills down 51 mmdiameter blastholes in fans 2 m apart. Eachstope yields between 25,000 and 35,000 t ofore.

KEMI, FINLAND


Atlas Copco Cabletec L installing cablebolts at Kemi.

RR3/RC12 19/7/05 10:14 Page 107

Tests showed that drilling upwardswould be about 30 per cent more efficient,but because of safety issues related to thepoor rock conditions, it was decided tostart with downhole drilling while gettingexperience with the rock and the miningmethod. Meantime, Kemi has ordered aSimba L7 C rig with a long boom to bedelivered in August, 2005. With the M6 Cand L7 C, operators will be able to coverall kinds of drilling patterns.

Mining of the 20 m wide secondarystopes will start in 2005, while sub-levelcaving with uphole drilling will be testedat one end of the main pit in 2006.

Secoroc rock drilling tools are used forproduction drilling. The previous 64 mmholes over-fragmented the ore, but a switchto 51 mm resulted in lower specificcharges and better fragmentation, whileretaining the same number of holes. Whendeveloping the secondary stopes, the minemay well go back to 64 mm drilling ifthere are problems keeping the holes opendue to the stresses and rock movements.

Kemi is carrying out slot hole drillingwith a Simba M4 C rig mounted on aScania truck. The front part of the rig hasbeen redesigned to accommodate theSecoroc COP 84L low volume DTHslothammer, which is used to drill the 305mm-diameter opening hole for the longholeraises. The blasting holes are drilled offusing a COP 54 with 165 mm bit with thesame tubes. The 20-m raises are blasted intwo 10-m lifts.

Rig Remote Access

The drill rigs at Kemi are integrated intothe Ethernet WLAN communications net-

work that eventually will cover the wholemine. Currently, this 1 GB network,which is based on commercially availableequipment, covers the declines, the work-shops and parts of the production area.

This network infrastructure not onlyallows effective underground commu-nication but also means that all theAtlas Copco drill rigs equipped withthe Rig Remote Access (RRA) optionare logically integrated into the informa-tion systems in Outokumpu’s administra-tive organization. The RRA is installedon the Rocket Boomer and Simba rigs.

The RRA, which consists of a communi-cation server on-board the rig and a net-work adapter, integrates with the mine’snetwork to allow data transfer and remotemonitoring and troubleshooting. It works asa two-way communication system, sincedata can be sent and received in real-timebetween Atlas Copco and the mine. Forinstance, should one of the drillrigsencounter a problem, the warning seen bythe operator will also be shown in the mineoffice, which can then contact Atlas Copcoimmediately, enabling them to enter therig’s electronic system and diagnose thefault.

The RRA’s main benefits are: theadministrative system can be updatedautomatically with the latest informationwith no manual handling; the rig operatoralways has access to the latest productionplanning; no need to write work reportsafter each shift, since all log files areautomatically saved to the planningdepartment; instead of forcing workorders to be written before each shift,they can be issued during the shift anddirected onto the specific drillrig; andfault diagnostics can be conductedremotely, which allows the service tech-nician to diagnose the problem andchoose the correct spare parts beforetravelling to the drillrig.■

Acknowledgements

Atlas Copco is grateful to Juha Riikonen,manager of the underground mine for hisassistance in arranging the site visit andreading draft. Contributions by EsaLindeman, open pit manager, HeikkiPekkarinen, concentrator manager, andJukka Pitkajarvi, chief geologist ([email protected]).

KEMI, FINLAND


Inside the 350 m level workshop atKemi.

RR3/RC12 19/7/05 10:14 Page 108

Lotschberg Alignment

The 34.6 km-long Lotschberg base tunnel,which has been developed from a numberof access points, is in an advanced stage ofconstruction, and will be ready for use in2007.

From the base of the 1.5 km-long, 67 sqm Mitholz access adit, located about 8 kmfrom the north portal site at Frutigen, three

main running tunnels are contracted toSatco, a joint venture led by Strabag withVinci, Skanska, Rothpletz & Lienhard, andWalo Bertschinger.

The east and west tubes have beendriven by drill/blast some 8.7 km south-wards, to meet faces coming north fromFerden. At the same time, the east tube hasbeen advanced some 7.5 km northwards tobreak out at the Frutigen portal. The westtube from Frutigen portal has also beendriven 800 m to junction with the east tube.

The nominal cross-section of excavationof the main running tunnel faces is approx-imately 65 sq m, depending upon therequired support, with a maximum of 280sq m at junction caverns.

These have been advanced usingsophisticated three-boom and basket AtlasCopco Rocket Boomer XL3 C drillrigsequipped with ABC Regular semi-auto-matic boom control with two control sys-tems, operated by two drillers workingfrom separate panels. Drillplan data istransferred from the planning office to themachines on PC cards.

The big Rocket Boomer XL3 Cs werebacked up by a pair of twin-boom AtlasCopco L2 C drillrigs, which handled work

LOTSCHBERG, SWITZERLAND


Satco reached Frutigen portal 8 months ahead of schedule.

Wolfgang Lehner, project manager forSatco at Mitholz.

Repairing Squeezing Ground at MitholzFlexibility of Purpose The Satco joint venture, under techni-

cal sponsorship of Strabag, installed

a complete purpose-designed excava-

tion system at their Mitholz contract

on the Lotschberg base tunnel in

Switzerland.

Speed and efficiency were the key

elements of a successful project, for

which Satco chose Atlas Copco

Rocket Boomer XL3 C drillrigs with

ABC Regular semi-automatic boom

control for production drilling, and

Rocket Boomer L2 C twin-boom

machines for the smaller-section

work. The rigs were equipped with

Secoroc rock drilling tools, and

Swellex rockbolts were used for

immediate support. This combination

of job-matched Atlas Copco equip-

ment, together with first-class on-site

maintenance support, helped Satco

to get six months ahead of contract

schedule over a period of three years.

However, close to the boundary of

the contracted distance south, the

faces unexpectedly hit soft carbonif-

erous banded deposits, some 1,400 m

beneath the Lotschen summit. Huge

ground pressure was transmitted to

the tunnel lining, causing compres-

sion and distortion of the steel arch-

es. Satco used its Rocket Boomer XL3

Cs to install 16 m-long MAI SDA self

drilling anchors to stabilize the strata

for replacement of the steel arches,

overcoming a difficult support prob-

lem.

RR3/RC11 26/6/05 11:06 Page 109

such as bolting, cross passage develop-ment, and extraneous excavation.

Standard Swellex rockbolts, in 3 m and4 m lengths, were installed as immediatesupport, normally at 1.5 m spacing in theroof and shoulders of each drive. All of theancillary face equipment such as trans-formers, ventilation extensions, and cablereels were carried on backup platformssuspended on rails slung from the roof.

This arrangement afforded maximummanoeuvring room for the large numbersof mobile equipment in operation.

When in good rock, each full, 8 m-widex 8.5 m-high arched face was drilled outby a Rocket Boomer XL3 C to 4.5 m depthusing Secoroc model–37 48 mm, 9-buttonballistic bits with R35 thread.

Between 105 and 120 holes were nor-mally required, together with two 102 mmbreaker holes in the centre. Averagedrilling rate was 3 m/min, and face androckbolt drilling took around 3 hours innormal ground. The rock generally com-prised good, hard limestone, which couldbe screened and crushed for aggregate.Total volume of excavated rock wasaround 1.8 million cu m, of which some700,000 cu m is being reused.

Excavation and Mucking

All blasting at Mitholz utilized site sensi-tized emulsion (SSE) explosives suppliedby Dyno Nobel Sweden. The profile holeswere charged at 50% density to controloverbreak, and the blasted faces weresafened using an excavator-mounted rockscaler. Overexcavation of 45 cm width onhorseshoe section and 60 cm width on cir-cular section was required to accommodatesqueezing under normal circumstances. AnLHD equipped with 5.4 cu m side-tippingbucket carried the spoil back to a 1,000 t/hmobile crusher located some 50-100 mbehind each face. From here, the crushedrock was delivered by a 330 m overlapstage conveyor to a 300 t/h trunk convey-ing system, and thence to a handling plantclose to the adit bottom where the rockwas further crushed to –200 mm, withoversize scalped by a grizzly. Verticalpocket elevators carried the spoil 20 m upto the adit conveyor loading points, fromwhere two 400 t/h tubed belt systems tookit to the surface for transport to the nomi-nated stockpiles.

The south section is serviced by two2,700 kW air conditioning units which arecooled by 150 lit/sec of recycled ground-water, and fresh air is supplied by a pair of2.4 m ventilation ducts. The air is con-tained by automatic roller shutter doors,and driven around the faces by auxiliaryfans. The Frutigen TBM tunnel is the mainfresh air intake and, by the time that the airreaches the south faces, most of it has trav-elled more than 15 km. All told, there are



Atlas Copco Boomer XL3 C drilling MAISDA to repair squeezing at Mitholz.

Torqueing up a 16 m-long grouted MAI SDA.

RR3/RC11 26/6/05 11:06 Page 110

in excess of 120 km of pipelines installedunderground for various purposes.

Support and LiningThe roof and sides of each excavatedround were shotcreted and 20-30 Swellexrockbolts installed, using a Rocket BoomerXL3 C to drill the 38 mm holes. Rockcover varies from 1,000 m to a maximumof 2,000 m beneath the Mitholz peaks. Insqueezing ground, wire mesh and steelfibre reinforced shotcrete were used.Rockbursting was a hazard at the far southend of the alignment, especially wherecrystalline rock was encountered.

Permanent lining comprises 250 mm-thick cast in-situ concrete formed over adrainage membrane, with the crown of thetunnel positioned 7.2 m above the top ofthe rail track. The main tunnels are beingfinished to a standard 62 sq m cross-sec-tion.

The site worked a 7 day/3 shift opera-tion, with four crews of 9 or 10 men rotat-ing on each face. Tunnelling progress waswell ahead of schedule when the southfaces reached the predicted water-bearingkarstic limestone, the drillrigs havingadvanced 250-300 m/month on each face,with a maximum achieved of 343 m/month.A complex probe drilling system using250-300 m-long cored holes was employedto investigate conditions ahead of the face,and average water inflows up to nearly 100lit/sec were experienced, with a maximumpressure of 54 bar. Hydraulic testing andground probing radar were also used, and agrouting regime established.

Carboniferous Encounter

In April, 2004, some 1.5 km before thesouth faces reached the boundary of theSatco contract, a section of softer rock wasencountered. This was accompanied bywater over a 400 m length, followingwhich the faces progressed through firstgranite, then limestone, sandstone andshale, before entering an unexpected 600m-long carboniferous section, in whichthin seams of anthracite appeared in theshale. At this point, Satco modified theexcavated section from arched profile tocircular profile.

They had been setting six 6 m-longgrouted rebars and four or five 4 m-longSwellex bolts for each metre of advanceusing the arched profile. For the circular

profile, they introduced R32 MAI SDA in8 m and 12 m lengths at a density of tenper metre of advance to replace the groutedrebar. By the end of June, 2004 the groundconditions had deteriorated to the extentthat fifteen 8 m-long R32 MAI SDA, eight12 m-long MAI SDA, and seven 4.5 m-long Swellex were necessary for eachmetre of advance.

Stronger rock reinforcement wasrequired, and it was decided to upgradefrom R32 to R38 MAI SDA, in a mix of 8m and 12 m lengths. This unprecedenteddensity of support sometimes reached 350m of rockbolting for each metre advance.

Nevertheless, squeezing caused defor-mation over a 100 m-long section close tothe face of each drive, causing a pause inadvance while the situation was assessed.Each face was secured using 12-15 off 4m-long fibreglass bolts, and a 470 m-longcored exploratory hole drilled to probethe ground ahead. This indicated that the



MAI SDA under installation alongsidereplacement steel arch.

Shotcreting a repaired section in thesouth drives.

RR3/RC11 26/6/05 11:07 Page 111

carboniferous section would run out afteranother 50 m in the west face and 10 m inthe east face, following which there would bea transition to comparatively good sandstone.

It was decided to reline the deformedtunnel in sections 50 m-long, installing

circular steel compression arches at 1 mintervals. For each arch, 16 off 16 m-longgrouted R38 MAI SDA were installedradially in 4 m-long coupled lengths in 76mm holes, both to stabilize the strataaround the tunnel and to pin the arches inplace. These were grouted in place at 20-40 bar pressure.

Once the relining was completed, tun-nelling operations resumed, and weresoon into good rock. Satco is carrying onbeyond the original contract southernboundary for more than an extra 1 linearkm of drive awarded as a bonus for earlycompletion.

North Completion

In the north, probeholes were maintained40 m ahead of the face, drilled in thecrown by one of the Rocket Boomer XL3Cs equipped with a RAS rod addingsystem. Detection of methane would trig-ger a warning system on the drillrigs, andthe monitoring system on the suspendedbackup would switch off HT electrics if adangerous concentration were encoun-tered.

Tunnelling at the north face was com-pleted in May 2003, some 8 months aheadof programme, as a result of which Satcowas awarded a further contract to excavatesome 800 m of the west tube from theFrutigen portal. All cross passage excava-tion between the east tube and the TBMtunnel is now complete.

The main concrete lining operationwent well in the north drive, where pair of12.5 m formworks returned 25 m/day ofcompleted lining. Concrete lining is pro-ceeding apace in the south drives.■

Acknowledgements

Atlas Copco is indebted to Satco andAlptransit Lotschberg for permission topublish this article and, in particular, toWolfgang Lehner of Strabag, project man-ager at Mitholz, for his assistance withinterviews and site visit.



Buckled arch with emergencyretaining bolts.

Section of Lotschberg tunnel fromFrutigen to Raron. The unexpectedarea of soft sedimentary rock isdelineated by red dotted lines.

Tungsten carbide bit used along with EYY type withMAI SDA at Mitholz.

25002000150010005000

2500200015001000500

0

Mithollz lateral adit

Ferdenlateral adit

NorthFrutigen portalm.s.l.

SouthRaron portal

m.s.l.

Steglateral adit

ADELRAIN EGGESCHWAND ST.GERMANLÖTSCHBERG LÖTSCHENTAL

ELSIGHORSE-GRAT

RR3/RC11 26/6/05 11:07 Page 112

Lower Development

In order to mine below the 800 m level, themine uses three Kiruna Electric trucks forore and waste haulage to the main crusher.A Simba M4 C longhole drilling rig isused on production, drilling up to 40 m-long x 76 mm or 89 mm-diameter blast-holes. The machine produces some 50,000drillmetres/year, while an older Simba1357 drills a similar number of metres inthe 51-64 mm range. The mine is soimpressed with the stability of the SimbaM4 C rotation unit that it has had an oldSimba 1354 rebuilt to incorporate the sameunit. A Simba M7 C is being delivered forcable bolt drilling. The drilling consum-ables are supplied by Atlas Copco Secorocunder contract. The ramp will be drivenfrom the current 980 m to the 1,100 m level.

An Atlas Copco Rocket Boomer L2 C isused on ramp and sublevel development,where the requirement is for 18 rounds/week

on a 2 x 7 h shift basis. The mine has anoption to purchase a second twin-boomRocket Boomer, this time an M2 C, whichis the mining version of their existing L2 C.

Rock Reinforcement

The mine installs up to 20,000 resinanchored rockbolts each year, and, havingupgraded its production process, found thatbolting became the new bottleneck. Afterprolonged testing of the latest Atlas CopcoBoltec LC, they ordered two units.

Using these machines, the workingenvironment for the bolting operatives hasimproved immeasurably, since the continu-ous manual handling of resin cartridgeshas been eliminated. The Boltec LC is afully mechanized rockbolting rig withcomputer-based control system for highproductivity and precision. The Zinkgruvanmodels feature a new type of magazineholding 80 resin cartridges, sufficient forinstallation of 16 rockbolts before refill. Itis equipped with a stinger, which appliesconstant pressure to keep it stable at thehole during the entire installation process.The operator can select the number of resincartridges to be shot into the hole, forwhich the rig air capacity is excellent.

Vital Combination

The Rig Control System (RCS) features aninteractive operator control panel with

ZINKGRUVAN, SWEDEN


Mechanized Bolting atZinkgruvanPartners in ProductionZinkgruvan Mining AB, Sweden’sthird largest mining company, is apart of Lundin Mining Corporation.Zinkgruvan Mining produces zinc andlead concentrates for shipment tosmelters in northern Europe.

The mine has been continuously inproduction since 1857, and ore outputnow stands at about 835,000 t/year,together with 185,000 t of wastefrom development.

Production is obtained from openstopes where, following difficultieswith seepage from hydraulic fillwhen rock quality diminished, themine now uses paste fill. Rather thandeepen the main hoisting shaft, themain ramp access was developedbelow the 800 m level, and willbottom out at 1,100 m under presentplans. Key to Zinkgruvan productionefforts is equipment supplied byAtlas Copco, which includes fourSimba production drillrigs, threeRocket Boomers and two Boltec rigs,together with maintenance and con-sumable supply contracts.

Atlas Copco Rocket Boomer L2 Cdeveloping the sublevels.

RR3/RC13.qxd 23/6/05 11:27 Page 113

full-colour display of the computer-baseddrilling system. Automatic functions in thedrilling process, such as auto-collaring andanti-jamming protection, as well asimproved regulation of the rock drill, pro-vide high performance and outstanding drillsteel economy. There is integrated diagnos-tic and fault location, and a distributed

hydraulic system with fewer and shorterhoses for increased availability. Data trans-fer is by PC-card, which also allows serviceengineers to store optimal drill settings.

The MBU bolting unit on the Boltec LCfeatures a single feed system, utilizing acradle indexer at the rear end, and a robustdrill steel support, plus indexer for grout-ing, at the top end. It is equipped with alow-mounted magazine for 10 bolts,designed for maximum flexibility duringdrilling and bolting.

The COP 1532 rock drill is the shortestin its class, with modern hydraulic reflexdampening for high-speed drilling andexcellent drill steel economy. It has sepa-rately variable frequency and impactpower, which can be adapted to certaindrill steel/rock combinations.

The BUT 35HBE heavy-duty boltingboom is perfect for direct, fast and accu-rate positioning between holes. Largecapacity working lights, and a joystick-operated spotlight, ensure that the operatorhas outstanding visibility from his workingposition.

Profitable Collaboration

The Rig Control System (RCS), originallydeveloped for Boomer rigs, is now alsoinstalled on Simba and Boltec rigs, so themine benefits from the common concept.

Atlas Copco has total responsibility forall service and maintenance operations onits equipment at Zinkgruvan, and has threeservice engineers stationed permanently atsite. The company is also under contractfor the supply, maintenance and grindingof Secoroc rock drilling tools, overseen bya Secoroc specialist.

From the mine point of view, theybelieve they have profited by their collabo-ration with Atlas Copco, particularly in thefield testing of the new generation rigs.Early exposure to the capabilities of thesemachines has allowed them to adapt theirmining and rockbolting methods to thenew technology, giving them a head starton the savings to be achieved. ■

Acknowledgements

This article is based on a paper written byGunnar Nystrom. The editor also grate-fully acknowledges the inputs of JonasSodergren, Hans Sjoberg and ConnyOhman, all of Zinkgruvan Mining.

ZINKGRUVAN, SWEDEN


Atlas Copco Boltec LC installingrockbolts in a development drive.

Grinding Secoroc bits on a Grind MaticBQ2 machine.

RR3/RC13.qxd 23/6/05 11:27 Page 114

History

The Bolu Mountain Crossing is midwaybetween Ankara and Istanbul, and repre-sents the most challenging section of themotorway construction. Along this 20 km-long stretch, four important viaducts and along tunnel are under construction.

The Bolu tunnel is a twin-tube motor-way tunnel of about 3 km length, accom-modating three lanes per tube, linking thewestern Asarsuyu valley to the easternElmalik village, on the Ankara side. Theoriginal design featured five support class-es in the tunnel, and two at the portals,with an excavation area ranging between190 sq m and 260 sq m. The original staticdesign was by Geoconsult GmbH ofSaltzburg, Austria, and, for the worst rockcondition, involved preliminary excavationand backfill of bench pilot tunnels, a three-layer lining, and a deep monolithic invert.

Excavation of the tunnel started in1993, and, almost immediately, problemswere encountered with clays. When theDuzce earthquake occurred in 1999, astretch of about 350 m of tunnel collapsedbehind the eastern faces, and major

damage was done to the lining and invertof both tunnels. Consultants Lombardi SAwere brought in to analyze the seismicloads induced by the earthquake, whichoriginated at the North Anatolian Fault.These analyses examined the depth, direc-tional effects, soil amplifications and dis-tance from the seismic source, and a panelof experts was set up to study the results.

Active Faults

Two active faults were recognized along the tunnel alignment: the Zekidagiand Bakacak faults (Barka-W Lettis &Associates).

The Zekidagi fault dips at almost 90degrees, is approximately 6 to 8 km-long,and possibly intersects with the tunnelalignment at nearly right angles, aroundchainage 62+430 in the left tube and

BOLU, TURKEY


Atlas Copco Boomer drilling over theface for forepoling.

Plan of Astaldi section of the Istanbul-Ankara highway.

Seismic Tunnelling at BoluOvercoming NaturalDisasterThe attempt in the mid-nineties attunnelling through the Bakacak Faultnear the Turkish town of Bolu wasaborted following the massive earth-quake in November, 1999. Thiscaused the collapse of a section ofmined tunnel, which had been exca-vated with preliminary primary sup-port of soil nails and shotcrete.

The overall design has beenrethought, and the tunnel is nowagain under construction. Seismicprinciples have been applied to thisproject, which is crucial to comple-tion of the Gumusova-Gerede sectionof the important North AnatolianMotorway linking Ankara and Istan-bul. The design criteria have definedthe fault crossing strategy, and thepractical solutions involve the exten-sive use of Atlas Copco MAI SelfDrilling Anchors (SDA) as primarysupport.

RR3/RC14.qxd 23/6/05 11:28 Page 115

52+350 in the right tube, over a length of25 m to 30 m. It has a potential for smallfuture displacement in the range of 0.15-0.25 in an earthquake of magnitude 6 to6.25. This section of tunnel was linedaccording to the original design, and noparticular problems were experiencedcrossing the fault, although high deforma-tions were recorded.

The Bakacak Fault has been identifiedas a secondary fault in the step-over regionbetween the two major North AnatolianFault (NAF) branches in the Bolu region.This clay fault exhibits low potential forright lateral strike-slip displacements. It issome 10-45 km-long, composed of severalsegments ranging from 3 to 5 km-long, andrupture displacements of up to 50 cm canbe expected in an earthquake of magnitude6.25 to 6.5.

Two likely traces of the Bakacak fault,which dips at 40 degrees, were identifiedcrossing the Bolu Tunnel betweenchainage 62+800 and 62+900 at the lefttube, and 52+730 to 52+800 at the righttube, over a distance of about 100 m. Thisis precisely the zone where excavation wasproceeding at the time of the earthquake.

Crossing Active Faults

Basically, two strategies are feasible tomitigate the seismic risk induced to tunnelsby ruptures of active faults across thealignment. These are commonly referred toas over-excavation, and articulated design.

In the first case, the tunnel is driventhrough the fault with an enlarged crosssection. A double lining is installed, andfilled by a porous material, such as foamconcrete. If there is a fault rupture, theclearance profile is guaranteed by the gapbetween the outer and inner linings. Thismanner of protection, commonly used formetro projects, is limited by the width ofthe cross section that must be excavated,and will be most effective when a faultrupture is concentrated within a fewmetres.

The articulated design strategy, on theother hand, reduces the width of the liningsegments, leaving independent sectionsacross the fault, and for a distance beside the fault. In a fault rupture, themovement is concentrated at the jointslinking the segments, containing anydamage in a few elements, without uncon-trolled propagation.

The maximum length of any single ele-ment depends on several factors, such aswidth of the cross section, expected move-ment of the fault, compressibility of thesurrounding soil, and element kinematics.

Articulated design was selected as themost appropriate for the large cross sectionof the Bolu tunnel, and for the excavationgeometry that had already been defined.

Design Philosophy

When the Bakacak fault was recognized asactive, almost one year after the Duzceevent, the restoration of the original tunnelwas almost complete, and the shape andtype of the cross section adopted wasalready defined. The bench pilot tunnels ofthe original excavation had already beenbackfilled.

BOLU, TURKEY


Standard cross-section of Bolu tunnelshowing massive support.

Shotcrete operations underway in thetop heading.

RR3/RC14.qxd 23/6/05 11:28 Page 116

The segments geometry was defined byconsidering a ratio between length andwidth of the tunnel segment equal to onethird, resulting in an element length ofabout 5 m. This geometry kept the load onthe single crown segment below an accept-able threshold value.

For practical reasons, the length of thesegments was reduced to 4.4 m, with a50 cm joint gap at invert. This facilitatedretention of the original modular reinforce-ment cage.

Following a fault rupture, the tunnelwill act longitudinally as an embeddedbeam, whose extremities are displaced bythe lateral offset of the fault. The assump-tion made, justified by the geologists, isthat a rupture will be uniformly distributedacross the fault boundaries, with horizontaldisplacement. Therefore the shear strain inthe fault soil can be reasonably assumed asthe ratio between expected offset andwidth of the fault at tunnel level.

Up to rupture of the joints, the tunnelwill be sheared and bent by the soil as anembedded beam. Once the joint’s shearresistance is attained, each segment will befree to move independently, according toexternal loads.

The maximum acceptable shear resis-tance of the joint has been defined on anequivalent elastic model, with soil mod-elled as springs acting in compression. Adisplacement is gradually applied to theextremities, and the shear stiffness of thejoints is designed so as to reach the shearfailure of the joint before lateral overloadof the element cross section, or bendingfailure at extremities.

Reinforcement and Joints

Across the fault zone, different supportmeasures have been adopted. Of these, themost important is an 80 cm-thick concrete40 N/sq mm prefabricated concrete slabintermediate lining to be installed betweenthe primary lining and the inner lining. Thereinforcement bars have been placed onlyin the inner (final) lining and at invert,while the shotcrete and intermediate lin-ings have been fibre-reinforced.

The primary aim of the reinforcementdesign is to provide a high ductility to thelining. The allowable rotation has beenestimated, and compared to the estimatedrotation for the load conditions. This wasachieved by introducing stirrups at shear,

keeping the spacing below 30 cm, and alsoby introducing a light dosage of steel fibresin the concrete mix, or applying an equiva-lent double mesh layer. These measureswere installed within the fault, and up to adistance of 30-40 m from the fault borders.

The joints, at 4.2 m spacing, have beendetailed to prevent soil squeezing betweenthe segments, and to bridge the static soilpressure to the surrounding elements, butopposing a sufficiently low shear resis-tance in the event of fault rupture.

To provide ring closure of the joint atthe invert, a 0.4 m-thick fibre reinforcedshotcrete beam is applied to bridge thegap. At the crown, the regular 40 cm-thickshotcrete preliminary lining has beenassessed as sufficient.

The 50 cm-wide joint is filled by twolayers of concrete blocks, with a 10 cmlow density PS layer in between. A water-proofing membrane is installed below theconcrete block slabs and the invert.

In general, at the crown, three levels oflinings are installed: a shotcrete lining, anintermediary lining of poured concrete,and a reinforced final lining. The water-proofing membrane bridges the seismicjoint gap between intermediary and finallining. The joint opening in the final lininghas been enlarged to 70 cm, and the gapwill be covered by a steel plate, for thepurposes of ventilation and fire resistance.

The backfilled bench pilot tunnels wereheavily reinforced to provide sufficientabutment to the crown loads during theexcavation. These beams cannot be inter-rupted while excavating, so the cutting of

BOLU, TURKEY


Installing prefabricated concrete slabintermediate lining.

RR3/RC14.qxd 23/6/05 11:28 Page 117

the joint in the section can only be executedonce the invert is in place.

Excavation and Support

The Bolu tunnel has been advanced on anew alignment, which diverts around thecollapsed section. It is being driven fromnewly established faces within the aban-doned tunnel on the Istanbul side. A150 m-long cut-and-cover section wascompleted at the Ankara portals beforeexcavation work could commence fromthis end.

The weathered, faulted amphiboliterock, with up to 140 m cover, is broken upby a Krupp hydraulic hammer mounted ona Cat 235 excavator, then loaded into roadtipper trucks. The 7 m-high top heading isopened using 30 x 6 m-long forepoles overthe crown, under which three pieces of the

5-piece steel arches are set at 1.1 mintervals. Then 20 off, 12 m-long anchors,each comprising 3 x 4 m lengths of AtlasCopco MAI SDA, are drilled in and groutedusing an Atlas Copco Boomer drillrig. Theroof and sides are given a 40 cm-thickapplication of steel fibre reinforced shot-crete, and a 50 cm-thick steel bar reinforcedshotcrete temporary invert is installed.

The bench is then advanced 2.2 m ateach side, and the legs of the steel archesare installed, together with bolts and shot-crete. Two incremental advances of 4.4 mallow the invert to be excavated 5 m-deepover the full width of the heading, and thisis filled with mass concrete with two pre-fabricated steel reinforcement cages. A pur-pose-built, self-propelled stage conveyor isused to transfer the concrete from the fleetof 8 cu m mixer trucks. The invert concret-ing is maintained within 25 m of the face.

The total excavated area of the tunnel is160-200 sq m. Where the rock is particu-larly poor, a 60 cm-thick concrete slabintermediate lining is installed, and theannulus backfilled with concrete. This isfollowed by a mass concrete in-situ lining,using 150 sq m x 13.5 m-long self pro-pelled formworks. The final lining opera-tion is kept within 75-85 m of the face, toensure permanent support as early as pos-sible. Concrete is supplied from two plantson site with 80 cu m/h output capacity,backed by a 350 t cement storage silo.

Where necessary, very-heavy latticegirders are placed as temporary support,and these are cut away as soon as suffi-cient permanent support is in place.

The first tube breakthrough is scheduledfor August, 2005, with the second follow-ing before the end of the year.

The finished twin-tube tunnel willaccommodate three lanes of traffic in eachdirection, with vehicle cross passages at500 m intervals. ■

Acknowledgements

Atlas Copco is grateful to the managementof the Bolu project for permission to visitthe site, and to Olivio Angelini, GaetanoGermani and Aziz Õzdemir of Astaldi fortheir help and assistance in preparation ofthis article. Reference is made to Designand Construction of Large Tunnel ThroughActive Faults: a Recent Application by M Russo and W Amberg (LombardiEngineering), and G Germani (Astaldi).

BOLU, TURKEY


General view of the Bolu tunnel facewith invert pouring underway.

Heavy steel reinforcement of the 5 m-deep concreteinvert.

RR3/RC14.qxd 23/6/05 11:28 Page 118

Riga Coal Dock

Riga coal dock handles a million t/y ofcoal from the Kuzbas region of Russia, andis looking to expand its business by usinglarger ships, for which the harbour has tobe deepened.

It was necessary to anchor the existingdock walls to solid ground prior to thedredging operation, following which anew, deeper wall is being installed. AtlasCopco MAI anchors are being used as bothtemporary and permanent support for thesheet piling operation.

Their installation is being carried out bythe marine construction division of BMGS,a Latvian specialist contractor.

The first stage involved anchoring theupper section of the existing steel sheetpiles by drilling from a purpose-built bargefloating in the dock, an operation whichcarried on 24 h/day, 7 days/week wheneverthe dock was free. The barge had to betowed out of the way every time a coalship tied up.

At each anchor position, a 150 mm-diameter cored hole was drilled 1.5-2.0m into the dock wall to penetrate the

concrete cladding and the steel sheetpile. Then 47 m-long, 130 mm-diameterholes were drilled 40 degrees below hor-izontal through the surface sand to pene-trate the sandstone bedrock below. Eachdrillstring comprised a cross bit with 16x 3 m-long threaded MAI T76 bars and15 couplings. Continuous grout injectionwas carried out at 40-60 bar pressure inthe 4 h-long drilling operation, duringwhich retarders were used to keep thecement workable.

A week later, a plate and nut werescrewed onto the protruding end of eachanchor, and stressed up to 60 t. Some 120anchors were required for the first stage,and these were installed in a horizontal lineabove the high water mark at 3 m intervals.This allowed dredging of the dock from itsprevious depth of 10 m to 13.5 m. Eachanchor was pull tested at 90 t.

Sheet piling operations then took placeduring the winter 2004/2005, along the lineof the new dock wall, which is around ametre seawards from the previous position.The annulus between the two walls isbeing concreted.

The second stage of anchoring is beingundertaken in 2005, using the same princi-ples as for the first stage. In this case, the

BALTIC STATES, NORTHERN EUROPE


Stabilizing Foundations in Baltic CitiesAncient and ModernThe Baltic States of Northern Europe

have done well to preserve most of

their historic buildings, some dating

from the Middle Ages. However, subsi-

dence is now the main enemy in Riga,

Latvia and Tartu, Estonia, where the

race is on to underpin the buildings

most affected. This is being accom-

plished with minimum intrusion using

micropiling techniques, in which MAI

SDA and grout pumps are the key ele-

ments. Similar techniques are also

being used to great effect in Riga coal

docks, where the sheet piling of the

dock wall is being secured using long

grouted SDA while the harbour is

deepened. The diversity of these jobs

highlights the flexibility of MAI SDA as

an essential construction tool.Barge-mounted drillrig installing 48 m-long MAI SDA anchors at Riga docks.

RR3/RC15 24/6/05 14:02 Page 119

new row of anchors will be drilled betweenthe earlier anchors on the same line,spaced at 3 m apart. This will result in 240permanent 47 m-long ground anchors at1.5 m intervals along the dock wall.

Dredging work can then be carried outwithout fear of the dock wall moving, andthe dock will be deepened from 13.5 m to

15 m. The anchors have been designed fora 40-year life expectancy.

Micropiling For Support

The Old City of Riga, much of whichwas constructed in the Middle Ages, isbuilt upon riverine deposits of theDaugava flood plain, using wooden pilesas foundations. When installed in a water-saturated environment, wooden piles willlast indefinitely because oxidation isinhibited.

For six hundred years, the water table inRiga Old City was stable. Then, in the1960s, a hydro dam was built across theDaugava River some 20 km upstream ofRiga. Since then, the water table has fluctu-ated, revealing the tops of the woodenpiles, and allowing oxidation. The oxida-tion has promoted rot, and the affectedbuildings have started to sink. The sinkinghas not been uniform, resulting in tiltingaccompanied by severe structural cracking,and differential subsidence along thefacades.

Halting subsidence of old buildings isnot easy, because access is usually diffi-cult, streets are narrow, and working placesrestricted. This is the precise scenario forwhich micropiles were developed, and asituation in which MAI anchors and groutpumps prove their value.

The theory behind micropiling for sup-port is very simple, seeking to create ahigher friction in the existing foundationsof the building. This is accomplished bydrilling and high pressure groutingthrough, or in the vicinity, of the base ofthe structure, to produce crosspiles to sup-port the base of the building.

The micropiles are formed by the intro-duction of grout during the drilling opera-tion. The grout pressure is designed tocreate piles of the required diameter,while the grout itself stabilizes the holeduring the drilling process. Addition ofaccelerators or retarders allows theinstaller to vary the set of the groutaccording to the specific ground condi-tions, and to ensure that the penetration issufficient to produce a good pile withoutwastage.

The micropiles are generally drilledtight to the building and as vertical as pos-sible, with a lookout angle of 15 degreesor less. A small crawler rig is generallyused, and the grout pump can be remotely



Schematic of drillrig mounted onfloating platform to drill downward intothe harbour wall.

MAI 400 grout pump at work in Riga basement.

Inlet grouting

Coupling T76Sheet pile

Concrete Soil

Grouting

Drillbit ø 130 mm

Pre drilled at ø 150 mm

FLOATING PLATFORM

Anchored rodT76, 3 m - longCutter

Adapter H55-MAI T76

The 47 metre-long Atlas Copco MAI Self-DrillingAnchors are drilled through concrete, sheet pilesand into the bedrock, strengthening the dockwalls prior to deepening the harbour.

RR3/RC15 24/6/05 14:02 Page 120

situated, possibly conveniently close to thecement storage.

The pullout force for a micropile is lessthan its load bearing capacity, so ahydraulic testing jack can be used to checkthat any pile has achieved its designcapacity, without influencing its function.

Overall, micropiling offers a dependable,fast, low-technology, and low intrusionmethod of underpinning buildings, andthe drilling techniques used penetrateboth wood and masonry without prob-lems.

MAI Self Drilling Anchors

The MAI SDA self drilling anchor,although designed primarily to operate intension, is ideally suited to the require-ments of micropiling.

For drilling purposes, MAI fully-thread-ed pipe can be cut into any suitable length,using couplings for extension. This allowsthe system to be installed in even the tight-est situations. Once a hole has reached therequired depth, the pipe, couplings and

disposable bit are simply left in the hole,reinforcing the finished pile.

Grout is mixed in an MAI M400 pumpon which the pressure and quantity can bevaried to suit the job. The machine’s gal-vanized frame and stainless steel charginghopper guarantee corrosion protection andwithstand the toughest treatment, and thepump itself is easy to dismantle for clean-ing and maintenance. The self drillingaspects of the MAI SDA system allowdrilling in unconsolidated or non-cohesivesoil which would otherwise requirecasing, and the hollow rod permits simul-taneous drilling and grouting through anadapter, speeding up pile installation. Theleft-handed standard rope thread acceptsstandard drill tooling, and can be suppliedin a variety of diameters and threads.

Generally, if the designer has done hisjob correctly, and the right diameter ofanchor and drillbit are used, the groutingeffectiveness can be gauged visually by theappearance of grout at the collar of thehole.

Saving Riga

FORE, a leading Baltic micropiling con-tractor, has underpinned a number ofancient buildings and office blocks in RigaOld City.

To support the new Hotel Man-Tess,FORE installed 200 micropiles to 8-9 musing MAI R38. The 200 year-old adjacentbuilding was supported by 114 mm steel



Installing MAI SDA using a handheld pneumaticjackhammer.

Atlas Copco ROC 712HC used by FOREto install MAI SDA.

RR3/RC15 24/6/05 14:02 Page 121



pipes installed to 8 m depth at half-metrespacing using an Atlas Copco 712HC drill-rig, and filled with concrete. These werethen secured using 15 m-long MAIanchors drilled at 7 degrees from horizon-tal, each providing 30 t of anchoring force.

At Pikadilija Café on Valnu Iela, closeto the Opera House, the six-storey struc-ture has been subsiding into the very softdeltaic riverine deposit, and needed stabi-lization before refurbishment. Theground is non-supporting, and themicropiles are designed to take the wholeweight of the building at around 20-25t/unit.

Located on the same street as PikadilijaCafé, the Terranova building has beenunderpinned by FORE using 350micropiles formed from MAI R38 selfdrilling anchors to 9 m depth grouted usingan MAI M400 grout pump at 25 bar pres-sure. Work was undertaken from both thestreet and basement of the building to pro-duce crosspile support.

In Valnu Street, FORE installed 350micropiles in the basement of the existing

block, which is being converted to officesand flats. The piles are 15 m deep and 15degrees from vertical, and designed to passthrough the mud layer and penetrate 1 minto the sand layer beneath. MAI R38 SDAgrouted by an MAI M400 grout pump pro-duced high friction piles.

A 14th Century grain warehouse inAldaru Iela was underpinned by FORE in2002 using MAI R38 SDA to producecrosspiles. The subsidence was arrested,and the building, situated close toParliament House, was refurbished.

In a totally different application, FOREis installing MAI R38 8 m-depth groutedanchors to provide stable foundations fornew high-voltage electricity pylons cross-ing Riga docklands.

Preserving Tartu

Tartu City Hall has been successfullyunderpinned using micropiling techniquesdeveloped by local contractor Mikrovai,and installed using Atlas Copco MAI SDAself drilling anchors.

L above: Ancient warehouse in Old Rigawas saved by underpinning.R above: Subsidence was arrested onthe six-storey Pikadilja Cafe.

RR3/RC15 24/6/05 14:02 Page 122

Mikrovai commonly installs 10-12 m-long piles using a 210 mm conical bit andsquare section pipe, and uses MAI SDAT76 hollow threaded bar for longermicropiles up to 18 m, with bit diameter upto 130 mm.

The City Hall was underpinned in 10weeks using a crew of 8 men. Some 514holes were drilled and grouted at 20 barpressure, using a total of 3,100 m of R32and R38 MAI SDA hollow threaded barwith 76 mm bits.

Generally, the R32 micropiles werecredited with 15 t bearing weight, andthe R38 with 30 t. The subsidence atthe City Hall has been successfullyarrested, and minor refurbishmentworks are now being undertaken withconfidence.

Also in Tartu, an old student dormitoryblock is being refurbished as a sciencedepartment for the University. Mikrovaiunderpinned the basement foundations byinstalling 230 off 6 m-long R32micropiles using MAI SDA. These weredrilled at 15 degrees from vertical bothinside and outside the building. Ifmicropiling were not available as aproven foundation underpinning tech-nique, this building would probably havebeen knocked down rather than refur-bished.

At the crossroads in Tartu city centre, alarge shopping mall is being constructedby the local Skanska company, for whichtemporary works include a steel sheet piledretaining wall to the high side of the slop-ing site.

Here Mikrovai has installed 42 off,14-18 m-long R32 MAI SDA and 20off, 16-18 m-long R38 MAI SDA toanchor the wall to the sandstone sub-strata. By drilling at 10 degrees belowhorizontal, the anchors, spaced hori-zontally at 4 m intervals along theupper wall section, can penetrate 4 minto the sandstone. The MAI hollowthreaded bar has been used in 4 mlengths, with 76 mm EX bits. The R32anchors have been tested at 20 t andthe R38 at 40 t.

Because the more traditional wirerope anchors require a casing system ofdrilling, they take longer to install andare more expensive for this type of job.Once the permanent retaining wall isbuilt, the temporary wall will becomeredundant and the anchors will be cut

and the sheet piles withdrawn forreuse.

Mikrovai has found that the drillbitis critical to a good job, and poorchoice can adversely affect the costequation. A too-small diameter drillbitwill result in a smaller grout columnthan required, and a too-large diametermay cause the hole to collapse. Also,they find that the drilling operationmust not be carried out too quickly,because the grout column has to formproperly, and this takes a certain timeaccording to the ground characteristicsof each job. A rule of thumb wheninstalling 15 m-long anchors is 15-25holes/day/rig, if access is not a prob-lem. MAI produces a full range of dis-posable bits in diameters for everycondition.■

Acknowledgements

Atlas Copco is grateful to Valery Zagulin,chief of BMGS geotechnical department inRiga, Dainis Musins, managing director ofFORE, and Urjo Eskel of Mikrovai fortheir help and assistance in the formula-tion of this article. Thanks also to NilsHellgren, managing director of Geomek,representative agent for MAI products inthe Baltic States.



Imposing City Hall at Tartu wasunderpinned in 10 weeks using 3.1 kmof MAI SDA.

RR3/RC15 24/6/05 14:02 Page 123

DAVENTRY, UNITED KINGDOM


Daventry Development

The main development contractor atDaventry is a joint venture of ThomasVale Construction (Site Manager DaveCasey) and Westpoint Construction,tasked with building 26 houses, five pairsof flats and two bungalows on the site.The housing development is on a wedge-shaped, sloping site comprising a relative-ly soft clay mix which, if developed byconventional means, would probablynecessitate the excavation and construc-tion of expensive deep foundations for thehouses and service roads. As facilitated bythe MAI Anchor soil nailing method, thesite has been terraced with embankmentssupporting the service roads at the end ofthe gardens of adjacent new properties.The soil nails are installed by drilling intothese embankments at 15-20 degrees. Asubstantial development cost saving willresult.

At the lower end of the site local condi-tions over a short length did not permit thecreation of an embankment, so here theMAI SDAs were inserted directly into alevel surface which would eventually be

covered up to form the gardens of some ofthe new properties.

Most UK inland soil nailing applica-tions are classified by geotechnical engi-neers as low-risk, lightly loaded, passiveinstallations with a design life of 60 or120 years. Exceptions are coastal areaswhere the effect of saline water is signifi-cant, or in other aggressive ground condi-tions.

Setting out the embankments in thecentral part of the housingdevelopment. In the background soilnailing is progressing on the sectionalready marked out.

MAI SDAs Increase Land Usefor English Housing Support for NewHousingIn the UK soil nailing represents the

vast majority of the market for self-

drilling anchors and housing develop-

ment forms a large part of market

growth.

At the Admirals Way housing devel-

opment in the English Midlands town

of Daventry, Atlas Copco’s UK MAI

distributor, Dywidag Systems

International, has been supplying

geotechnical specialist contractor

Keller Ground Engineering with hol-

low-bar MAI anchors for clay sub-soil

stabilization.

Keller also recently carried out sim-

ilar work at Snodland, Kent to stabi-

lize chalk and clay

Installing soil nails in one of thedevelopment service roadembankments.

RR3/RC19B 18/8/05 13:52 Page 124

MAI SDAs

The self-drilling anchors used by Keller atDaventry were of the R32N hollow rope-threaded bar design with 100 mm-diame-ter, open-face, retroflush sacrificial drillbits suitable for clay. The left-hand threadallows connection to standard drill tooling.The bar, measuring 32 mm diameter overthe threads or effectively 29.1 mm has anultimate strength in this size of bar of 280kN and yield strength 230 kN.

MAI SDAs can be installed in unstableground without the need for temporary holecasing by simultaneous drilling and grout-ing. Depending on the type of bit used, theyare suitable for a wide range of groundmaterials including soft clay (as atDaventry), sand, gravel, inconsistent fill,boulders, rubble, and weathered and frac-tured rock.

Installation

At Daventry, the consulting engineer’sground reinforcement pattern called forsoil-nail lengths of 5-13m depending ontheir position on the site. This is achievedby using coupling sleeves to connect thestandard lengths of threaded bar. In all750-760 soil nails are being installed atAdmirals Way.

A surveyor first lays out each portion ofthe site to be reinforced using red-paintedmarkers to indicate the planned entrypoint for each soil nail according to thedesign of the consulting geotechnicalengineer.

Keller used two of their own crawler-track, hydraulic, rotary drilling rigs toinstall the SDAs, generally with the boom

inclined 15-20 deg and at right angles to thetracks, permitting the rig to be driven alongthe row of soil-nails to be installed. Thedrill bit and rotation speed are chosen toensure that the borehole is cut rather than



Keller Ground Engineering’s SiteAgent, John MacGregor Jr., views theinstallation of some of the last soilnails to be installed in the lower partof the site.

Building from foundations commenceswith the completed embankmentreinforcement in the background.

Reinforcement is complete with alayer of geomat secured by SDA nutsand plates holding fine wire mesh.

RR3/RC19B 26/6/05 10:44 Page 125

displacing the soil through percussiveaction or a high feed pressure. This ensuresbetter permeation of the grout and thus abetter bond.

Each rod section of the soil nail, three orfour metres long, takes only about fourminutes to insert using rotary percussivedrill action and a 3-man crew. There is adrill-rig operator, another to act as ‘spotter’and to insert the MAI SDAs and extensionsas drilling progresses, and a grout mixerand pump operator. Simultaneous withdrilling a cementitious grout is pumped at2.1-4.1 bar (30-60 lbf/sq.in.) through a special

injection adaptor and thence through thehollow bar of the SDA. The use of large,100-mm bits enables a sufficiently largegrout column to be created to meet thespecification.

Once the soil-nails are inserted correct-ly into the ground, sheets of weldedheavy wire mesh are attached to the pro-truding SDAs, followed by a layer ofgeomat, non-woven, geosynthetic materi-al incorporating a layer of lighter wiremesh. The facing components are held inplace by the galvanized plates andthreaded nuts of the SDAs. This all actsmainly as erosion control of the stabi-lized surface, but also aids the stability ofthe whole installation.

Keller’s John MacGregor reported that,on the Admirals Way site, the geotechnicaldesign called for ten ‘test’ soil nails acrossthe site to which tension was applied oncethe grout had cured. Dywidag’s ownStressing and Testing Services Departmentcarried out all the testing work. A tempo-rary bearing platform is installed since thetest load would otherwise be pullingagainst a soft (clay) face, albeit overlainwith geogrid etc. The test establishes thetrue capacity of the soil nail bond in the sta-ble zone rather than including the effect ofthe wedge zone.

Prestige Housing

Keller Ground Engineering carried outwork on another housing development in2004. The Woodlands Farm luxury hous-ing development at Snodland in Kent,south-east England, represents an impor-tant application for embankment soil nail-ing to make the best use of landscaping.Keller Ground Engineering, working forBerkeley Homes, used 473 R32N MAISDAs to create an embankment betweenthe building area and a lake in an old chalkpit. The soil nails were 10 or 12 metrestotal length.

Keller employed a drill boom and feedmounted on the long backhoe boom of ahydraulic excavator to install five rows ofsoil nails in chalk and clay from the top ofthe embankment. This allowed free accessfor a bulldozer to shape the bottom of theslope. After installing the soil nails thehead plates and nuts were used to retain ageogrid layer of mesh and geosyntheticmaterial to allow restoration withtopsoil.■



Installing the top row of soil nails atWoodlands Farm, Snodland, prior toexcavating the low part of the slope.

The completed slope stabilizationshowing the heads of the soil nailsand the geogrid later

RR3/RC19B 26/6/05 10:44 Page 126

First Toll Motorway

One of the leading projects is the UK’sfirst toll motorway, the BirminghamNorthern Relief Road; now known as theM6 Toll. The engineer working for theClient, Midland Expressway (M6),designed a steep wall in a cutting, protect-ing some existing trees. The use of slopestabilization with soil nails allowed the‘footprint’ of the cutting to be reduced (seepicture), hence reducing the necessary land‘take’ from the neighbouring landowner,saving project expenditure. On behalf ofthe main contractor consortium CAMBBA(made up of Carillion, Alfred McAlpine,Balfour Beatty and Amec), a specialistsub-contractor installed 1000 soil nailsusing MAI SDAs in a grid pattern acrossthe face of the cutting wall.

The ground drilled is sandy clay withoccasional boulders, necessitating the useof sacrificial drop-centre button bits withtungsten carbide peripheral blades to forma clean hole. The fully galvanized, R32Nhollow-bar, MAI SDAs varied in totallength from 7 to 12m with couplers.

Since this cutting construction wasmade in February 2003, the M6 Toll nowforms a valuable and busy alternative tothe previous congested routes of the oldM6 and A5 linking the south-westMidlands of England to the North West,by-passing the Birmingham/Black Countryconurbation.

Stabilizing Freight Route

Britain’s transport infrastructure alsoincludes many kilometres of rail routes, thestructures of which often require attention,since many are over a century old. Onerecent rail project involving MAI SDAs,678 in all, was the stabilization of a failingembankment on the Crewe-SalopIndependent Line in the centre of theMidlands town of Crewe in October 2004.

Network Rail (North West) and itsEngineer considered the more convention-al solution of sheet-piling the lower part ofthe embankment, but this may haverequired lengthy closures of a busy railroute, a deeper structure requiring moresite investigation, and some other environ-mental disturbance such as from noise.Using the alternative of soil nailing onlylimited access from the top of the embank-ment was required.

UNITED KINGDOM


Cutting during construction of the M6Birmingham Northern Relief Roadshowing the (right) wall stabilized byMAI SDA soil nails compared with(left) a more conventional low-anglecutting slope requiring more surfacearea and volume of excavation.

Soil Nailing Infrastructure alongEngland’s RoutesA Major Force inTransport Slope StabilizationThe UK distributor for MAI

International, Dywidag-Systems

International, has been leading the

way in slope stabilization using MAI

self-drilling anchors, in conjunction

with Atlas Copco Construction &

Mining (UK). Some of the most pres-

tigious recent transport construction

and renovation projects in the UK

have benefited from the use of the

MAI SRN hollow-bar anchor system

(Self-Drilling Anchors - SDAs), chiefly

for soil nailing, whether for stabiliza-

tion of cuttings walls or embank-

ments.

RR3/RC19A 23/6/05 11:39 Page 127

The soil-nail reinforcement was designedin accordance with the new European soil-nailing Standard EN 14490, and employedR32N MAI hollow-bar of 16-m length. Onlythe top-bar (down to the coupler) needed tobe galvanized against atmospheric corrosionin order to preserve the structural integrityfor the design life of the installation.

Two drill booms were used, mounted onhydraulic excavators with long-reach (22-m) ‘sticks’. This enabled the soil nails to beinstalled in the embankment in an ‘under-arm’ action, leaving the rail lines below tobe operated as normal and without distur-bance to neighbouring structures. Thedrilling equipment included a shank inte-grated into the injection adaptor enablingsimultaneous drilling and grouting.

Badger Bother

Other Midlands rail projects have been car-ried out in Railtrack’s (now Network Rail)Midland Zone. Two embankments on the

TSV Line near Henley-in-Arden had beensuffering gradual subsidence due to both thetype of fill material used and the activities ofbadgers burrowing in the embankments. Theeffects of this on the track necessitated theimposition of a 20-mile/h (32-km/h) speedrestriction on train movements.

Using a series of one-way gates, thebadger population was ‘rehoused’ nearbybefore other rectification work began. Trialsoil nails were first tested by Dywidag’sStressing and Testing Department to establishthe bond stress of the nail within the stablezone of the slope, behind the slip plane.

Following successful trials a specialistcontractor installed the SDAs in bothembankments. The method, includingsimultaneous drilling and grouting,enabled the reinforcement to be installed inthe unconsolidated sand and gravel withoutresort to hole casing, whilst also reducingoverall installation time. Following com-pletion of the soil-nail grid, the slope sur-face was reprofiled, and rail speedrestrictions could be lifted.

Also in the Midlands, there was a majorslip in the Beehive Embankment on theWest Coast Main Line in Leicestershirethat needed to be rectified in February2004. The slip had been caused by thepresence of a perched water table. Thesolution involved drainage of the perchedwater table and the installation of threerows, with 100 soil nails in each, usingR32S galvanized MAI SDA hollow bar.The head plates of the SDAs also serve tohold a layer of geosynthetic material inplace to deter surface erosion.

Nailed Gabions

In March 2003 the Earlswood Embankment,on the main London-to-Brighton railwayline, required major stabilization work forthe Southern Zone of Network Rail. TheClient’s engineers chose a solution combin-ing a layer of gabions immediately under thetrack with embankment slope soil nailing.Gabions are cuboid steel-wire-mesh basketsfilled with rocks to form, with neighbouringunits, a self-draining wall.

The contractors used MAI SDAs to fixthe gabions in position to form a platformunder the track, and also inserted the seriesof soil nails in the underlying embankment.The embankment works were extensive,requiring a total of 1500 soil nails formedby R32N MAI hollow bar. ■

UNITED KINGDOM


The restored embankment on theLondon-Brighton line at Earlswoodshowing the soil-nailed gabions justbelow the rail level

On the Crewe embankment slopeinstalling soil nails with excavator-mounted drills. Note protruding headsof installed SDAs

RR3/RC19A 23/6/05 11:39 Page 128

Mixed Ground

The project designer for the undergroundwork is Geodata SpA of Turin, for theclient, a consortium known as Agency ofXX Winter Olympic Games of Turin 2006.

The contractor, Baldassini and TognozziSpA Costruzioni Generali of Firenze, Italy,is using drill/blast techniques in the rocksections of the alignment, and a hydraulichammer in the loose ground.

Rock reinforcement is required to improvethe quality of the rock, for which Swellex Mn16 rockbolts in lengths of 4 m and 6 m havebeen used for supporting the portal area.

Project Description

The project for the diversion of the Colledel Sestriere state road N23 is taking placenear the town of Porte, approximately 40km from Turin, in the upper ChisoneValley of the Piedmont Region.

In addition to embankments and drybridges along the river Chisone, twosingle-tube, bi-directional natural tunnelsare being built, La Turina with a length of601 m, and Craviale with length of 991 m.

La Turina tunnel is being driven partlyin rock and partly in softer ground, where-as the Craviale tunnel was driven entirely

in rock comprising gneiss-greenstone andgneiss mica-schist belonging to the meta-morphic substratum of the CristallinoMassif of the Dora Maira.

Swellex rockbolts were used bothunderground for primary support, and toreinforce the rock walls above the easternportals of the tunnels.

Slope Stabilization

The geo-structural survey carried out on theslopes housing the portals showed that the

PORTE-TURIN, ITALY


Reinforcement of the slope by theeastern portal of the La Turina tunnelwith 4 m-long Swellex Mn 16rockbolts.

Portal Stabilization UsingSwellexOlympic DeadlineImprovements are being made to the

state road EN23 near the town of

Porte, Turin in Italy ahead of the 2006

Winter Olympic Games. The project is

designed to relieve traffic congestion

in the town centre.

Tunnel alignment is in gneiss-

greenstone, mica-schist and glacial-

lake loose ground, so rock

reinforcement is critical to the suc-

cess of the project, particularly at the

portals. Based on its proven quality

and consistent performance, Atlas

Copco Swellex Mn 16 was selected as

the rockbolt for use in stabilizing the

rock around the portal.

Reinforcement of the slope at theeastern entrance of the Craviale tunnelusing 6 m-long Swellex Mn16rockbolts.

RR3/RC17 23/6/05 11:40 Page 129

rock was very altered and fractured. Theseslopes, analyzed using the empiricalapproach of Romana (1991), were classifiedas partially stable, and assessed as class III-SMR-Slope Mass Rating. They requiredimmediate support using rockbolts andmesh with shotcrete to avoid the potentialslide generated by a combined influence ofthe joints and inclination of the slope.

The formula of Palmstrom (1982) wasused to calculate the required number of

bolts based on the number of joints (Jv)per cubic metre of rock.

The bolt requirements indicated by thismethod were: length 3-6 m; distance betweenbolts 1-3 m; bolt strength 120-150kN; andresulting force applied a 120-150 kN/sq m.

To support the walls around the portals,Atlas Copco Swellex Mn16/Mn24 wereinstalled, being the rockbolts with thespecified features. Some 450 bolts of 6 mlength were used to stabilize the slope atthe eastern entrance of the Craviale tunnel,and around 200 bolts of lengths 4 m and 6m were installed to support the easternportal of Turina tunnel.

Since the sides were reinforced in this fash-ion, no blocks have moved and the entranceshave been stabilized and safely supported.■

References:

Palmstron, A., 1982. The volumetric jointcount – a useful and simple measure of thedegree of rock jointing. Proc. 4th Cong.Int. Assn Engng Geol., Delhi. Romana, M., 1991. SMR classification.Proc. 7th Congr. On rock mech SRM,Aachen, Germany.

PORTE-TURIN, ITALY


Swellex rockbolts stocked by theeastern entrance of the Cravialetunnel.

RR3/RC17 23/6/05 11:40 Page 130

Sitina, Bratislava

Contractor Banske Stavby is tunnellingunder low overburden in heavy, brokengranitoid rock using two Atlas CopcoRocket Boomers equipped with SecorocT32 Speedrods and 45 – 51 mm bits.Injection grouting is carried out using anMAI m400NT grout pump.

The client for the construction isSlovenska sprava ciest, and the designer isDopravoprojekt a.s, Bratislava.

Sitina tunnel comprises east and westtubes, each requiring 251 m of cut andcover at each end and 1,189 m of naturaltunnel in between. The natural tunnel isbeing driven at an excavated section of 79-98 sq m in crystalline rock comprisingbiotite and double-mica granodiorites withsporadic granites, often with veins or peg-matites up to 1.5 m-thick.

NATM techniques are used, with fivebasic rock classes. In classes 1-3, the exca-vation is divided into a top heading and

bench, and is carried out using drill/blast.In classes 4 and 5 an invert arch is added,and excavation is by mechanical means.Often, a combination of drill/blast andmechanical excavation is employed.Mucking out is by wheel loader into 25 tdumpers.

The crystalline rock at Sitina is inten-sively tectonically disrupted, with systemsof 1 mm-3 cm cracks and breaks which

SLOVAKIA AND CZECH REPUBLIC


Driving From Budapest toNürnberg Saving the Best UntilLastCompletion of missing links in the

European Motorway system is rapid-

ly producing fast connections

between the most unlikely places.

Key elements of the D2/D5 (E65/E50)

motorway from Hungary to Germany

are the 1.4 km-long twin-tube Sitina

tunnel in Bratislava, Slovakia and the

380 m-long Valik tunnel at Plzen in

the Czech Republic. These are difficult

tunnels, which is perhaps why they

have been left until nearly last to be

completed. Both are using advanced

rock reinforcement techniques to

drive through incompetent rock with

low overburden. Swellex, Symmetrix,

Boodex and MAI SDA are all

employed to keep these jobs moving

in the right direction, together with

Atlas Copco drillrigs and Secoroc

drillsteel and bits.

Grouting rockbolts from the basket ofthe Rocket Boomer 352.

Atlas Copco Rocket Boomer L2 C facedrilling at Sitina south.

RR3/RC20 23/6/05 11:46 Page 131

can be up to several metres wide, and filledwith clay material or breccia or mylonite.Locally, coarse blocks of schist-biotiteparagneiss of several tens of metres inthickness occur, locked tectonically intothe granitodiorites. These discontinuitiesresult in rock splitting to produce largeblocks which can fall from the roof andsides of the excavation.

The primary lining uses wet shotcretewith a non-alkaline accelerator, latticegirders, mesh and 4-6 m-long groutedrebar rockbolts.

The main faces are advanced as topheadings, with benches trailing at 50-120m behind. The 51.7 sq m top heading ismicropiled through lattice girders to pre-vent falling ground, and shotcreted prior toinstallation of 4 m-long grouted rebar bolts

radially, using one of the Rocket Boomerdrillrigs. The bench is advanced to producea full excavated section of 105 sq m. Thelattice girders comprise three pieces in thetop heading, to which legs are bolted as thebench advances.

The ground conditions may demand any-thing from 80 x 1.5 m-deep blastholes usingplastic explosives with millisecond delaydetonation in the harder sections, to excava-tor-mounted hydraulic hammer or scalingbucket in the softer sections. There is a seri-ous blasting vibration restriction, due to theproximity of the Slovak Academic Institutewith its sensitive technical laboratory equip-ment. Therefore continuous monitoring isnecessary, and parameters are modified tocounter undesirable effects.

Symmetrix ComplementsBoodexUmbrella drilling has been neededthroughout the alignment to date, due tothe shallow overburden and soft, blockymylonite. Initially, 12 m-long pipes, com-prising 4 x 3 m lengths of perforatedBoodex, were drilled in with a pilot bit anddisposable crown. These were grouted for10 minutes at 20 bar pressure to produce aconcrete column around each pipe. With25-33 pipes in each top heading, the grout-ed columns formed complete umbrellasbeneath which it was possible to excavatein 0.8 m increments. Usually eight incre-ments were advanced, and eight arches setand shotcreted, beneath each umbrella,leaving a 5.4 m overlap beneath which thenext umbrella could be safely drilled.

Lately, Symmetrix has proved cheaper,more reliable, and faster than Boodexwhere rock conditions have been particu-larly poor, and some 20 Symmetrix 12 m-long umbrellas have been installed, eachcomprising 15–20 boreholes.

Whereas Boodex employs a pilot bitwith a following reamer, which enlargesthe hole to allow the casing to be pushedin, the Symmetrix system uses a rotatingcasing with rock cutting crown behind thepilot bit. Hence Symmetrix providesimmediate support for the hole, making itbetter in very poor ground conditions.

Forepoling with up to 40 x 4 m-long, 25mm-diameter rebar rods is used in theworst ground conditions.

In the areas of the main tunnels wherethe five crosspassages are being excavated



North portals of Sitina with east falsetunnel nearing completion.

Symmetrix system umbrella drilling atSitina portal.

RR3/RC20 23/6/05 11:46 Page 132

between the tubes, the invert is concretedto a depth of 1.5 m, and for 10 m on eitherside. A similar depth of concrete has alsobeen laid at the ends of each of the tubes.

Valik, Plzen

Valik tunnel is situated about 30 km fromthe German border on the Czech Republicsection of the Prague-Nürnberg motorway.Overall length of the tunnel is 380 m, com-prising 330 m of natural tunnel, with 20 mof cut-and-cover at the west end and 30 m ofcut-and-cover at the east end. There is also a900 m-long surface cutting at the east end toconnect with the advancing motorway.

The natural tunnel is complicated byshallow cover and a very narrow corridorof surface rights beneath which it has to beexcavated. The twin tubes have to beextremely close together, requiring buttressto be excavated and replaced in entirety

with reinforced concrete before the maintunnel drives could commence.

The central pilot tunnel, within which thereinforced concrete buttress for the maintunnel was constructed, was excavated fromthe west end within a 4.5-month timespan.It was driven as a 4 m-high top heading and2 m bench, using an Atlas Copco RocketBoomer L2 C, one of two at site. Main con-tractor Metrostav also has one Atlas CopcoRocket Boomer 352 at Valik, together withfour GIA DC16 service platforms based onAtlas Copco carriers.

Excavation was in increments of 0.8 m,1.0 m, and 1.2 m, depending upon the spe-cific ground conditions, and lattice girderswere set at similar intervals. In very softground, an excavator with scaling bucketor hydraulic hammer was used instead ofthe drillrig.



Atlas Copco Rocket Boomer L2 Cstarting south tube at Valik tunnel.

Symmetrix or Odex?

Both Symmetrix and Odex can be usedfor drilling holes up to 273 mm diameter,when the choice of bit will depend uponthe specific ground conditions, the pres-ence of rock and boulders, and the rig tobe used.

For shallow holes in soft ground, Odexis cheaper to use, a little slower, willrequire more torque, and may deviate ifhard boulders are encountered.However, a skilled driller will overcomethese conditions.

Symmetrix is generally used with DTHhammers, but can also be used with tophammers such as the COP 1838 forsmall diameter holes for applicationssuch as umbrella drilling where thelower torque requirement can be crucial.

Both Symmetrix and Odex can be usedwith all standard casings, and also withHPDE, PVC and fibreglass casings.Drilled casings are becoming increasing-ly popular in underground construction,especially in urban areas, where they aretending to replace pile driving and pipejacking in ground containing boulders.In these conditions, Symmetrix is oftenthe only method that can penetrate suc-cessfully, and is sometimes called uponto drill down to 100 m.

Valik tunnel west end showing south,pilot and north tube excavations.

RR3/RC20 23/6/05 11:47 Page 133

Immediate support was provided by 4m-long Atlas Copco Swellex Mn12 rock-bolts, with shorter 3 m versions being usedin the stronger rock sections. Some 3,000of the longer units were installed, alongwith some 2,000 of the 3 m version. Up to25 Swellex bolts were installed for eachmetre of advance, with shotcrete beingapplied systematically to roof and side-walls, and to the face when necessary.

Concrete Buttress

The construction of the concrete supportbuttress between the two tubes of the maintunnel required foundation works throughfour separate soft ground sections, com-prising a total of 90 linear metres. Toimprove the footing in these areas, 6 m-deep micropiles were installed in rows offour and three at 1 m spacing.

This work was undertaken by a specialistsubcontractor, who drilled 123 mm vertical

holes in the floor of the pilot tunnel, andinstalled two heavy rebars into each holebefore pouring concrete to complete thepiles in-situ. The revealed ends of therebars were hooked, in order to provide asecure connection for the main buttressconcrete reinforcement.

Likewise, the crown of the pilot drivewas reinforced by installation of 4 x 6 m-long grouted rebars per metre of advanceto key into the buttress reinforcement.

In order to establish the east portals, an18 m-deep pipe umbrella was installed,together with 6 m-long face anchors. Abeam support was also necessary immedi-ately above the east portals, secured by 17x 20 m-long grouted cable anchors.

Main Tunnels

Main tunnel excavations are being under-taken sequentially using NATM tech-niques. This involves top heading andbench excavation of the outside shouldersof each tube using lattice girders, MAI selfdrilling anchors SDA R 25 150kN in 3 mand 4 m lengths, and shotcrete.

The north tube is being developed inadvance of the south tube. Depending onthe geology, up to 27 SDA are beinginstalled into each fan or profile, with a 1m distance between fans.

This is followed by two-phase excava-tion of the upper sections of each tube toform the main tunnel roofs, and then theremaining bench can be removed to con-struct a curved invert. During the process,the area above the concrete buttress isbeing grouted for consolidation, to promotetransfer of the ground pressure away fromthe main tunnel lining. The remaining ele-ments of the pilot tunnel lining are beingremoved on advance. The final lining of thetunnel will comprise reinforced concrete ofvarying thickness from 0.3 m to 0.5 m.

Sitina tunnel is on schedule to open fortraffic in August, 2006.■

Acknowledgements

Atlas Copco is grateful to Banske Stavbyengineers Vladimir Kotrik, Anton Sumerakjr and Anton Petko for permission toextract from their paper TechnologicalProcedure of Construction for the SitinaTunnel, and to Metrostav engineerMiloslav Zelenka, manager at Valik tunnel,for his assistance at site.



Section of Valik tunnel showingconcrete buttress between maintubes.

Buttress formworks inside Valik pilottunnel.

RR3/RC20 23/6/05 11:47 Page 134

Grouting Contract

The contract differentiated between sys-tematic and sporadic grouting, with pay-ment according to work and materialquantities. The main components were:drilled metres for investigation; groutingand check holes; quantities of cement;numbers of packers; and the working hoursfor the grouting operation.

The systematic grouting procedure aslaid out in the contract included following:31 holes of 18 m-long; bottom of the holehas to be 5-6 m outside the tunnel contour;and distance between two covers is set at10 m, or two blasting rounds.

In Scandinavian tunneling, leakage fig-ures are most important and are used to

guide the grouting operation. Leakagemust be measured and recorded, and leak-age per drill hole must not exceed 10lit/min. The grouting stop pressure is set at35-45 bar.

Leakage<100 l/min drillhole. Stop pres-sure 40-50 bar and be standing for 5 min.

There is a difference between leakageper/min/100 m tunnel and leakage/min/drill hole.

In Sweden, the leakage/min/100 m oftunnel the most important, while inNorway leakage/min/drill hole is morepopular.

The total inflow of water in the tunnelwas measured at 14.9 l/min/100 m. Thespecification was set at 7 lit/min/100 m.

Pore pressure measurements showedthat, with the grouting undertaken andwith some infiltration, the groundwaterlevel could be maintained at the samelevel as before tunnel construction com-menced.

OSLO, NORWAY


Systematic Grouting at Oslo SubwayHalf Century ProgressThe T-Baneringen project is the

biggest enlargement of the Oslo

Subway since the system got under-

way in the 1960s. It comprises sever-

al new subprojects, of which the first

to be undertaken is the section from

Ullevål Stadium to Storo. The align-

ment of the 1.24 km-long tunnel, with

a cross-sectional area of 65 sq m,

passes through a very difficult zone

between sections 700 and 750, which

called for an intense grouting opera-

tion.

Contractor Veidekke chose the lat-

est grouting technology from Atlas

Copco Craelius to handle this chal-

lenge, where absolute control over

the efficiency of the grouting opera-

tion was key to its success. The

Unigrout EH 400-100-90 WBC

described in this report proved to be

the right machine for the job in every

respect.

Ramp entrance to Oslo Subway tunneldevelopment.

W:C ratio starts at 1.0Leakage figures < 500 lit/min/drillhole gives a W:C ratio = 0.8 Leakage figures < 1000 lit/min/drillhole gives a W:C ratio = 0.7Leakage figures <1500 lit/min/drillhole gives a W:C ratio = 0.6/0.5

RR3/RC23 24/6/05 13:33 Page 135

The grouting operation in this difficultsection 700-750 was accomplished in 21rounds compared with the 4-5 roundsrequired for the rest of the tunnel.

The corresponding figures for thecement consumption were 425,860 kgcompared with 50,000-70,000 kg for thestandard systematic method.

Craelius Unigrout EH-400

The Unigrout EH 400-100 -90 WBC usedin Oslo features two silos at the back of theunit, the small silo for bagged cement andthe large silo for 1,000 kg big sacks, or, asin this case, delivered by separate cementsilo trucks. Both onboard silos areequipped with vibrators, and the larger ofthe two also has an agitator level monitor,which sends a signal to the operator whenthe cement level is low. On the top of the

silo there are also a safety grill and a pro-tecting lid.

The electrical cable reel is locatedalongside the larger silo. On the right sideof the container there are two doors, onefor entry when the unit is not operating andthere is no hydraulic power, and the largerone for installation and removal of equip-ment.

The left side of the grouting containerfeatures a wall divided into two flaps, bothof which are operated hydraulically. Thelower part acts as a walkway during thegrouting operation, and the upper part actsas a protecting roof for the operator. On thesilo section there is also a foldable walk-way for the operator. On the forward endthere are protected connectors for thehoses.

An operative works from the elevatingbasket, placing the packers and grout linesin the grout holes in the order specified,while the supervisor controls the results atthe face.

The grouting operator carefully followsthe different steps in the production, pump-ing and placing of the grout. Every step isrecorded simultaneously on the Logac andthe WBP.

The grouting operator has full control ofall the equipment and recorders within anarms reach. He has three different opera-tion modes to choose from: grout for the

OSLO, NORWAY


Grouting Quantities for the 50 metre

section 700-750

Drill metres: 9,081 mMicro cement: 426,255 kgGrout Aid: 88,609 kgStandard cement: 81,234 kgGrouting time: 925 h Total cost: NOK6.5 millionGrouting cost/m: NOK125,000

Atlas Copco Craelius Unigrout EH400-100-90 WBC.

Working platform at the front of theUnigrout truck.

Grout control station.

RR3/RC23 24/6/05 13:33 Page 136

standard grouting operation; GIN for per-forming grouting according to the GIN(Grouting Intensity Number) method; andLugeon for water pressure tests. A roofover the control position protects him fromdripping water and falling rock particles.

The safety rack is folded in when thetwo flaps are unfolded, and the lights in thecontainer roof reflect against the walls toprovide good visibility for the grouters.

Consultants set the GIN values based onthe rock parameters for the maximum pres-sure, maximum volume/m/drillhole, andthe allowed GIN max curve.

They report that logging of the groutingoperations and feedback from the LOGACprograms is a tremendous improvement. Thequantities of cement per time unit for every

single hole and for every water cement ratioare recorded, together with the start and stoptimes of grouting. The pressure history forevery drillhole is also available.

Weight Batching

The electronic weight batching processorDosac SV 6804 is a compact modular-built, micro-controlled unit specificallydesigned for use on systems utilizing straingauge load cells.

It automatically weighs water, cement 1and cement 2 on scale 1, and admixture 1on scale 2 and admixture 1 on scale 3.

All weighing can be done simultaneous-ly. All instructions for weighing, emptying,

order receipts and mixing times are con-trolled by the formula system.

The mixer is suspended on three straingauge load cells.

The Pumpac hydraulic control blockhas levers and knobs for the high pressureand low pressure valves and knobs for theflow setting valves. Beside the hydraulic

control blocks are the hydraulic oilmanometers.

The Cemix 403 HWB mixer containeris supported by three load cells which sendthe weight information to the WBP, whichalso controls the two admixture tanks

OSLO, NORWAY


Logac displays information about worksite and hole data.

Worksite: 10 digits availableSection: 10 digits availableHole No: 2 digits availableHole length: 3 digits + one dot(comma) digitStage number: 3 digits availableRecipe No: 2 digits availableInjection round no: 1 digitFile Name: A specific number for each and every hole

Typical Logac screen dump.

Controlling overall grouting operation.

Pumpac hydraulic control.

Cemix with two admixture tanks.

RR3/RC23 24/6/05 13:33 Page 137

hanging on load cells and the water inletvalve.

Admixture Control

The different types of admixture are sup-plied from 1,000 lit-capacity containersstanding beside the Unigrout. Two pumpssend the admixture up to two separate spe-cially-designed distribution containers sus-pended on load cells for very accuratemeasurements. The load cells are moni-tored by the Dosac processor.

A High Pressure Cleaning hose reel isplaced next to the cement inlet for easyaccessibility.

Cement input is through a separatemoisture-proof, dust-proof connectionoffering protection from splashed water.

A special 300 lit-capacity water tankand booster pump are used for improvingon the water filling speed.

A good grout must be mixed accordingto specification and standard of cement,admixtures and other additives. There is aconsiderable difference in mixing OrdinaryPortland Cement and microcement, and theadmixtures also alter the quality of thegrout considerably.

Agitation and Delivery

The three-way distribution valve ishydraulically operated from the opera-tor’s panel, and the ready mixed groutcan be directed to either of the two sepa-rate Cemags or to dump. Grout quality

can be different in each of the three agita-tors.

At the Oslo Subway job, Veidekkechose to have two Cemags of differentsizes in order to be better prepared fordifferent qualities of grout. Both Cemagsare supported by load cells, with weigh-ing controlled by the operator from hispanel

Three Pumpac with 110 mm groutcylinders and standard ball valves areinstalled in the container, with room fora fourth pump above the third pump.Pumpac No 2 is installed above PumpacNo 1. All three installed pumps areeasily accessible for service, and eachcan be supplied with a manifold withseveral grout lines if required. A drippan under No 2 Pumpac collects anyspillage.

The grouting container is driven by twoPower Unit Grouting PUG 45s with 45 kWelectrical motors positioned to the frontoutside the container, in order to minimizeany noise and disturbance. The compressorwhich operates the air regulated valves andcylinders is located between the two PUG45s.

The hydraulic pumps are lowered intothe hydraulic oil in the tank beneath theelectric motors.■

For more info see the Atlas CopcoCraelius Selection Guide on the AtlasCopco homepage.

OSLO, NORWAY


Refilling cement silos.

PUG 45 power unit grouting.

Twin Pumpac 110 B units.

RR3/RC23 24/6/05 13:34 Page 138

ROCKBOLT SPECIFICATIONS


Pages 139-144 28/7/05 11:18 Page 139



Pages 139-144 28/7/05 11:18 Page 140



Pages 139-144 28/7/05 11:18 Page 141



Pages 139-144 28/7/05 11:18 Page 142



Pages 139-144 28/7/05 11:18 Page 143



Pages 139-144 28/7/05 11:18 Page 144



Pages 145-147 28/7/05 11:21 Page 145



Pages 145-147 28/7/05 11:21 Page 146



Pages 145-147 28/7/05 11:21 Page 147



Pages 148-151 28/7/05 11:26 Page 148



Pages 148-151 28/7/05 11:26 Page 149



Pages 148-151 28/7/05 11:26 Page 150



Pages 148-151 28/7/05 11:26 Page 151

ANCHOR BOLT SPECIFICATIONS


Pages 152-163 28/7/05 11:30 Page 152



Pages 152-163 28/7/05 11:30 Page 153



Pages 152-163 28/7/05 11:30 Page 154



Pages 152-163 28/7/05 11:30 Page 155



Pages 152-163 28/7/05 11:31 Page 156



Pages 152-163 10/8/05 8:51 Page 157



Pages 152-163 28/7/05 11:31 Page 158



Pages 152-163 28/7/05 11:31 Page 159



Pages 152-163 28/7/05 11:31 Page 160



Pages 152-163 28/7/05 11:31 Page 161



Pages 152-163 28/7/05 11:31 Page 162



Pages 152-163 28/7/05 11:31 Page 163

DRILLRIG SPECIFICATION


Main specifications

Recommended hole range for ROC D5R32,T38,T45 35-89 mm 13 /8"-31/2"Hole depth 28 m approx.92'Recommended hole range for ROC D7T38,T45 64-102 mm 13 /8"-4"T51 89-115 mm 31/2"-41/2"Hole depth 28 m approx.92'T51 21 m 69'Hydraulic rock drills ROC D5COP 1238MEImpact power,max. 12 kW 16 HPCOP 1838 LEImpact power,max. 16 kW 22 HPHydraulic rock drill ROC D7COP 1838ME/HE,COP 1840Impact power,max. 18 kW 24.5 HPCompressorAtlas Copco C 106 screw compressorWorking pressure,max. 8.5 bar 125 psiFAD 85 l/s 180 cfmorWorking pressure,max. 10.5 bar 152 psiFAD 105/127 l/s 215/270 cfmEngine ROC D5/D7Caterpillar Diesel CAT 3126BRating at 2200 rpm 131/149 kW 176/203 HPBoom-0,1 Folding boomFuel tankCapacity 280 l 73 US gal.Feed Feed length,total 7140 mm 24'Travel length 4240 mm 15'Feed extension 1400 mm 4'3"Feed force,max. 20 kN 4400 lbfTramming Tramming speed,max. 3.1 km/h 2.0 mphTractive force 110 kN 2500 lbfHill climbing ability 20 ° (30 ° with winch)Track oscillation ± 12 ºGround clearance 455 mm 171/2"Transport dimensions ROC D5/D7Total weight,approx. 11700/13000 kg 25700/29300 lbWidth 2370 mm 7'10"Length 10710 mm 35'2"Height 3100 mm 10'2"

Visit www.surfacedrilling.com for more information

Pages 164-65 10/8/05 9:15 Page 164

DRILLRIG SPECIFICATION


Main specifications

Recommended hole range for ROC D5R32,T38,T45 35-89 mm 13 /8"-31/2"Hole depth, 28 m approx,92'Recommended hole range for ROC D7T38,T45 64-102 mm 13 /8"-4"T51 89-115 mm 31/2"-41/2"Hole depth 28 m approx. 92'T51 21 m 69'Hydraulic rock drills ROC D5COP 1238MEImpact power,max. 12 kW 16 HPCOP 1838 LEImpact power,max. 16 kW 22 HPHydraulic rock drill ROC D7COP 1838ME/HE,COP 1840Impact power,max. 18 kW 24.5 HPCompressorAtlas Copco C 106 screw compressorWorking pressure,max. 10.5 bar 152 psiFAD at 10.5 bar 105 l/s 215 cfmEngine ROC D5/D7Caterpillar Diesel CAT 3126BRating at 2200 rpm 131 kW/149 kW 156 HP/203 HPBoom-11 Folding boom,cab versionFuel tankCapacity 280 l 73 US gal.Feed Feed length,total 7140 mm 24'Travel length 4240 mm 15'Feed extension 1400 mm 4'3"Feed force,max. 20 kN 4400 lbfTramming Tramming speed,max. 3.1 km/h 2.0 mphTraction force,max 110 kN 25000 lbfHill climbing ability (30 º with winch) 20 ºTrack oscillation ± 12 ºGround clearance 455 mm 171/2"Transport dimensionsTotal weight,approx. 12500-13600 kg 27500-30000 lbWidth 2370 mm 7'10"Length 10710 mm 35'2"Height 13100 mm 10'2"

Visit www.surfacedrilling.com for more information

Pages 164-65 10/8/05 9:15 Page 165

BOLTING RIG SPECIFICATION


Main specifications

Boltec 235H-DCSRock drill 1 x COP 1532/1132Bolting unit 1 x MBUBoom 1 x BUT 35HBDrilling system DCS 12-55Bolting system DCSCarrier DC 15CLength,excl.bom 6192 mmWidth with bolt rack 2205 mmHeight 2300 mmTurning radius 5800/3000 mmWeight 16600 kg

Pages 166-171 10/8/05 9:18 Page 166



Main specifications

Boltec SLRock drill 1 x COP 1028Bolting unit MBU 16SLBoom 1 x BUT 32SLDrilling system EDSLength,tramming 10000 mmWidth 2480 mmHeight,carrier 1300 mm

roof min/max 1300/1700 mmTurning radius 6180/3550 mmWeight 12800 kg

Pages 166-171 10/8/05 9:18 Page 167



Main specifications

Boltec MCRock drill 1 x COP 1532/1132Bolting unit 1 x MBUBoom 1 x BUT 35HBDrilling system RCSBolting system RCSCarrier L-seriesLength,tramming 13156 mmWidth,excl .bolt rack 2210 mmHeight,standard 3010 mmTurning radius 6500/3600 mmWeight 21600 kg

Pages 166-171 10/8/05 9:18 Page 168



Main specifications

Boltec LCRock drill 1 x COP 1532/1132Bolting unit 1 x MBUBoom 1 x BUT 35HBEDrilling system RCSBolting system RCSCarrier L-seriesLength,tramming 14096 mmWidth,excl bolt rack 2510 mmHeight,standard 3100 mmTurning radius 7650/4450 mmWeight 26000 kg

Pages 166-171 10/8/05 9:18 Page 169



Main specifications

Cabletec LCRock drill 1 x COP 1838/1638Boom 1 x BUT 35BBFeed 1 x BMH 210-seriesDrill steel support BSH 55Rod handling RHS 17DControl system RCS -Drilling

RCS -Cable installationRCS -Cement handling

Carrier L-seriesLength,tramming 14042 mmWidth,excl bolt rack 2710 mmHeight,standard 3100 mmTurning radius 7500/4550 mmWeight 28000 kg

Pages 166-171 10/8/05 9:18 Page 170

SCALING RIG SPECIFICATION


Main specifications

Scaletec LCHammer 1 x SB 300 ScalerBoom 1 x BUT SCControl system RCSCarrier M-seriesLength,tramming 13828 mmWidth 2196 mmHeight,standard 3010 mmTurning radius 6500/4000 mmWeight 21000 kg

Pages 166-171 10/8/05 9:18 Page 171

DRILL RIG SPECIFICATIONS


Pages 172-173 28/7/05 11:38 Page 172

DRILL RIG SPECIFICATIONS


Pages 172-173 28/7/05 11:38 Page 173

HYDRAULIC DRILL SUPPORT


BSH 110-SDA Kit

Basic kit includes control panel,mounting kit andbushing halves.Bushing halvesFor Anchor rod R25 3128 2021 23For Anchor rod R32 3128 2021 22For Anchor rod R38 3128 2021 21For Anchor rod R51 3128 2021 20COP Conversion kitFor COP 1238 3128 3124 80For COP 1838 3128 3124 79For COP 1440 3115 3129 90

Pages 174 10/8/05 9:21 Page 174

ROCKDRILL SPECIFICATIONS


Pages 175-177 28/7/05 11:41 Page 175



Pages 175-177 28/7/05 11:41 Page 176



Pages 175-177 28/7/05 11:41 Page 177

HYDRAULIC FEEDS


Pages 178-79 28/7/05 11:44 Page 178

HYDRAULIC FEEDS


Pages 178-79 28/7/05 11:44 Page 179

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 180

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 181

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 182

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 183

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 184

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 185

OVERBURDEN DRILLING


Pages 180-87 30/7/05 12:08 Page 186

OVERBURDEN DRILLING


Symmetrix Overburden Casing System

The patented Symmetrix system can drill straight holes atany angle, including horizontal, and to depths

beyond 100 metres.

Pages 180-87 30/7/05 12:08 Page 187

GROUTING


Main specifications UNIGROUT EH400-100-135WB

Agitator 2 x CEMAG 203HWBAgitator 4 x CEMAG 402HGrout pump 4 x PUMPAC 110B BasicHydr.power unit 3 x PUG 45Length 12 mWidth 2.8 mHeight (transport) 3.9 m

(operation) 4.7 mLine voltage 690 VInstalled power 150 kWTotal weight 23 870 kg

Pages 188 10/8/05 9:22 Page 188



Pages 189 10/8/05 9:24 Page 189

DRILLING EQUIPMENT


THREADED.QXD 10/8/05 9:34 Page 190

DRILLING EQUIPMENT



DRILLING EQUIPMENT


Internet Guide

Atlas Copco divisions:www.atlascopco.com/rdewww.atlascopco.com/secorocwww.atlascopco.com/craeliuswww.atlascopcowagner.com

Link and Product pages:www.atlascopco.com/cmtportalwww.surfacedrilling.comwww.boomer-rig.comwww.copdrill.comwww.raiseboring.comwww.swellex.com

Atlas Copco Photo Archive:www.atlascopco.com/photo


DRILLING EQUIPMENT



DRILLING EQUIPMENT


Keep up to date with the world of mechanized rock excavation –

Visit Mining & Construction on-line atwww.min-con.com


DRILLING EQUIPMENT


SECOROC Grind Matic:How to spend less on Secoroc products

Drill bit designs


DRILLING EQUIPMENT


For a free subscription to Mining & Construction magazine visit

www.miningandconstruction.com


DRILLING EQUIPMENT


cont.


DRILLING EQUIPMENT



DRILLING EQUIPMENT


All current Atlas Copco Reference Booklets areavailable on CD-ROM.

To order, visit www.miningandconstruction.com


DRILLING EQUIPMENT


This issue of Rock and Soil Reinforcement

is also available on CD-ROM.

To order a personal copy visit

www.rock reinforcement.com


TAPERED EQUIPMENT


TAPERED.qxd 10/8/05 9:31 Page 204

TAPERED EQUIPMENT



TAPERED EQUIPMENT


156 exciting pages all about

Surface DrillingGet your own copy atwww.min-con.com

Button bit

cont.


TAPERED EQUIPMENT



TAPERED EQUIPMENT


152 exciting pages all about Face Drilling – Get your own copy atwww.min-con.com


Rock & Soil Reinforcement

third edition

www.rockreinforcement.com

Talking TechnicallyCase Studies

Product Specifi cations

a technical reference edition

Atlas C

op

coR

ock &

So

il Rein

forcem

ent

Th

ird E

ditio

n

The

face

of

inno

vatio

n

Supporting your business wherever you are

Atlas Copco MAIPhone: +43 4245 65 16 60 Fax: +43 4245 65 16 68 00

Atlas Copco supplies the widest range of advance cost-effi cient rock reinforcement solutions for mining and tunnelling, including fully-mechanized Boltec rock bolting rigs, Swellex rockbolts, and MAI self-drilling anchors.Each and every product has been designed to help maximize your tunnel advance and minimize costs per drilled metre – and always with the highest level of safety in mind.

Because we’re a global organization, we have the resources to be truly local. Find out more at www.atlascopco.com and select “Country”. Or give us a call. We’d be happy to listen to your requirements, and even happier to meet them.

www.atlascopco.com

Printed matter no. 9851 6283 01b

9851 6283 01b Rock Reinforcement complete.pdf

Documents

Transcript of 9851 6283 01b Rock Reinforcement complete.pdf