Filling the Gap – a Geomechanics Perspective

A U S T R A L I A N C E N T R E F O R G E O M E C H A N I C S

NEWSLETTER

The need for the project was identified aftera number of failures of barricades hadoccurred at various mines around the world,with each of these failures resulting ininrushes of backfill to working areas. Furtherinvestigation of previous studies also showedother areas where the mechanics ofunderground backfill were poorlyunderstood, such as why laboratorystrengths regularly tended to underestimatethe strengths achieved in situ, and the needfor development of a constitutive modelthat could facilitate modelling of miningprocesses involving fill.

Methods currently used for the calculationof barricade loads tend to be simplistic,including those that use ultimate strengths toestimate stresses in a stable fill mass, whereobviously ultimate strength is not mobilisedeverywhere. Particularly during the fillingoperations with fine grained material theapplication of these simple design

approaches is fraught with problems and hasnow been shown to be inappropriate(Helinski et al., 2006).The reason is that weshould not assume drained conditions (freedraining of excess pore water). In fact, inextreme cases very little drainage occurs andthere is therefore no consolidation of thepaste fill (this is known as the undrainedcondition).With no consolidation there willbe no arching.The consequence is that thefull hydraulic load of tailings could betransferred to the barricades, resulting inmuch greater barricade loads than thesimplistic (drained) approach would produce.

As an example of the importance of thisdistinction, Figure 1 illustrates the differencebetween adopting a drained or undrainedassumption on the total vertical stressdeveloped within a simple, hypotheticalstope that is 50 m high.The materialproperties adopted for the fill in both casesis that of a fully hydrated paste.

Filling the gap – ageomechanics perspective

By Andy Fourie, principal – environmental geomechanics,Australian Centre for Geomechanics,Matt Helinski, PhD student, University of Western Australia and

Martin Fahey, associate professor, University of Western Australia

The School of Civil & Resource Engineering at the University of Western

Australia and the Australian Centre for Geomechanics initiated a research

project that is aimed at improving the understanding of the geomechanics

of underground backfilling, ranging from applications of hydraulic fills

through to paste fills.

What’s in this Volume?

Filling the gap – a geomechanicsperspective ...........................................1

Field inventory of abandoned mines in Western Australia .................5

Testing and evaluation of corrosion of cable bolt anchors ...........................9

Open pit mine seismicity..................12

Pressure grouting – the end of insanity ............................................13

CSIRO researches open pit techniques...........................................16

Endeavour Mine shines with integrated geotechnical service .......18

Paste and Thickened Tailings ...........21

2006-2007 event schedule.................24

The views expressed in this newsletter are those of the

authors and may not necessarily reflect those of the

Australian Centre for Geomechanics.

Industry has witnessed an increased use of full-plant tailings as backfill. In some cases, cement and otherbinders are added to produce paste fill. Photos courtesy of St Ives Gold

Continued on page 2

V o l u m e N o . 2 6 M a y 2 0 0 6

Mine Closure 200613-15 September 2006

Perth, Western AustraliaAt Mine Closure 2006 attendees will

exchange views and expertise with theirpeers practicing the diverse range of

disciplines involved in mine closure activities: geotechnical,

environmental, social, financial andregulatory. Invited speakers include:Clive Bell, Aust. Centre for Minerals

Extension & Research; Gavin Murray, ANZBanking; Graham Cobby, Dept. of Industry

& Resources of WA; Ramanie Kunanayagam,Rio Tinto and Paul Dowd.

Early bird registration closes 31 July 2006.Contact the ACG to register

jo, should the contents reflect the subject title? page 12 differs

2 Australian Centre for Geomechanics • May 2006 Newsletter

The inset shows contours of total verticalstress (for a case where a barricade islocated in the bottom right-hand corner).The dashed line shows the maximum self-weight vertical stress (hydrostaticcondition) and as can be seen, theundrained result is extremely close to thisupper limit. In contrast, the drainedanalysis produces a variation of verticalstress with a depth that is much lowerthan these values.This example illustratedthat stress distribution is dominated bypore water pressures and that if placedundrained, even fully cured paste willgenerate very high stresses.

The importance of this effect is evenmore pronounced when the impact onthe barricade loads is calculated. Figure 2

shows this difference, with the drainedanalysis producing a barricade load ofonly about 80 kPa, while an undrainedanalysis produces a load of 800 kPa, i.e. adifference of one order of magnitude.

So which is the correct approach for atypical paste fill? It is probably true to saythat it will be somewhere between thetwo, but it is not possible to say that theloads will always trend towards either ofthe extremes.This depends on factorsthat are fill-specific and depend in additionon how the fill is placed, the use of restperiods, etc. In other words, simple rules-of-thumb are unlikely to be adequate untila more fundamental understanding isdeveloped that can be used to underpinsuch simplified approaches. A more

rigorous approach requires that theconsolidation process must be accountedfor, with the degree of stress transfer tostope walls developed as a consequenceof such consolidation. A preliminary studywas therefore undertaken using the one-dimensional finite strain consolidationprogram Mintaco that was developed atUWA for the modelling of consolidationof tailings placed at a high void ratio.

An initial analysis of uncemented backfillwas carried out as this was consideredthe most reasonable approach withexisting technology.The results from thisanalysis are nevertheless instructive.

A vertical stope, 30 m high, was modelled.The parameters for the model werederived from published data on paste fill.The simulated filling sequence included aninitial pour of an 8 m thick plug, followedby a curing period of 24 hours after whichthe remainder of the stope was filled at arate of 0.4 m per hour.The predicted totaland effective stresses and pore waterpressure were monitored at a height ofone metre above the stope floor. Theresults of this analysis are presented inFigure 3. As can be seen, virtually nodissipation of pore water pressureoccurred during the ten day process,which would result in very large barricadeloads and a completely unconsolidated fillmass.The lack of consolidation andinstability are issues that most tailingsengineers expect of a 30m high tailingsdam filled in ten days. It may be arguedthat the one dimensional nature of theMinTaCo doesn’t account for any stressredistribution (arching) to the surroundingrockmass. However, as shown in Figure 1in order to generate any of this archingconsolidation is required.

Figure 1 Predicted variation of vertical total stress along the centreline of a stope filled with uncementedtailings. Results are shown for the fully drained and the undrained condition

Figure 3 Consolidation analysis using uncementedtailings properties

Figure 2 Estimation of barricade loads using drainedand undrained analysis

Continued from page 1

Copyright© Copyright 2006.Australian Centre for Geomechanics (ACG),The University of Western Australia (UWA).All rights reserved. No part of this newsletter may be reproduced,stored or transmitted in any form without the prior written permission of the Australian Centre for Geomechanics,The University of Western Australia.

DisclaimerThe information contained in this newsletter is for general educational and informative purposes only. Except to the extent required by law UWA and the ACG make norepresentations or warranties express or implied as to the accuracy, reliability or completeness of the information contained therein.To the extent permitted by law, UWA andthe ACG exclude all liability for loss or damage of any kind at all (including indirect or consequential loss or damage) arising from the information in this newsletter or use ofsuch information.You acknowledge that the information provided in this newsletter is to assist you with undertaking your own enquiries and analysis and that you should seekindependent professional advice before acting in reliance on the information contained therein.

3Australian Centre for Geomechanics • May 2006 Newsletter

A review of soil and cement literaturerevealed a number of importantmechanisms that had to be incorporatedinto a model in order to adequatelyrepresent cemented fill behaviour.These were:

• increasing strength and stiffness due tohydrate growth,

• increasing strength and stiffness withincreasing density,

• reducing permeability with time,

• reducing strength and stiffness due tohydrate damage caused by overloadingat an early phase of strengthdevelopment, and

• self-desiccation, which is induced by thereduction in volume caused by thecement hydration process (Helinski etal., 2006).

Models were developed and verified(using experiments on both hydraulic andpaste fills) to represent the abovemechanisms.These models were thencoupled into a modified version ofMinTaCo known as CeMinTaCo (Helinskiet al., 2006).This model was comparedwith in situ data and shown to provide anexcellent representation of in situbehaviour (Helinski et al. 2006).Thesimulation summarised in Figure 3 wasrepeated, with the difference that 5%cement was added to the fill.Twoadditional lines are shown in Figure 4,which again represents the developmentof pore water pressure within thehypothetical fill.The middle line shows theresult when all of the above five factorscaused by cement hydration, except forself-desiccation, are included in the model.The lower, dashed line has all thesefeatures included, plus it includes a

simulation of the self-desiccation process.The differences resulting from accountingfor hydration and factors such as stiffnessincrease and permeability decrease (thelower line), are dramatic.The pore waterpressure (and by implication the loads onbarricades) is substantially reduced,peaking at a value of only about 210kPa,compared with the same fill, but withoutcement, where the peak stress was about480kPa.While it can be seen that thecharacteristics introduced due tohydrating cement can significantly increasethe degree of consolidation, it isimportant to appreciate that any changesin the mix (or this hydrating behaviour)can dramatically impact on consolidationbehaviour and therefore barricade loads.In an effort to demonstrate this, anotheranalysis using a cement content of 2%was undertaken.The results of thisanalysis are compared with those for 0%and 5% in Figure 5.

Figure 5 indicates that simply reducing thecement addition can create significantlyhigher pore water pressures that wouldresult in higher barricade loads. It shouldalso be noted that changes tocharacteristics such as density, rate ofhydration and self-desiccation will have asimilar impact on the consolidation andtherefore must be considered whenestimating barricade loads.

Unfortunately it is not possible to simplytake results such as those shown in Figure5 and extrapolate to other sites, because

of differences in fill type, particle sizedistribution, mineralogy and potentialdifferences in binder type and processwater. All of these factors can alter thecement hydration process and thus therate of strength and stiffness gain,permeability decrease and the degree andrate of self-desiccation.

There may be combinations of fill, binderand process water that appear to providestrength increases but have a negativeeffect on self-desiccation induced porewater pressure reductions. An examplebeing that the presence of excess silicadue to the addition of fly ash or silicafume can generate a reaction thatgenerates a volume increase (resulting inincreasing pore water pressures) ratherthan a decrease.Therefore, while thisbinder may appear to provide animproved result (when consideringstrength gain) they may have a detrimentalimpact on the in situ effective stresses.

Laboratory strengths versus insitu strengthsIt has been noted at a number ofoperations that the in situ strengths of acemented paste fill are invariably higherthan those obtained from laboratorystrength tests on otherwise identicalmaterial.The discrepancy may beattributed to the fact that curing of acemented soil under an effective stress(not total stress as suggested by someauthors) will increase strengths. It should,however, be noted that the time thiseffective stress is applied (with respect tocuring time) will impact on the result. Forexample, if the effective stress is appliedprior to the commencement of curing,the strength increase will be greatercompared with the application of stressafter the completion of hydration. As theapplication of effective stress will be equalto the dissipation of pore water pressurethis can only be calculated using a fullycoupled model such as CeMinTaCo.

A significant outcome of the researchalready undertaken is the development ofa simple sample preparation/curingFigure 4 The impact of cement addition on the

consolidation behaviour of a paste fillFigure 5 Impact of changes to cement addition


technique that can be applied to achievesamples that are more representative ofin situ material. It should however benoted that this type of preparationtechnique will only be suitable in somecircumstances.

Exposure stabilityAs mining progresses deeper and groundstresses increase, the need to undercut fillmasses increases. It is also frequentlynecessary to mine through a previouslyfilled stope. In order to address thesetypes of questions one needs to have aclear understanding of both in situ stressconditions as well as the materialconstitutive behaviour. Only byunderstanding the placement mechanics

can one begin to approach theseproblems rigorously.

Future workWork to date has concentrated ondeveloping a one-dimensional model thatadequately simulates the complexinteractions that take place in a fillundergoing simultaneous consolidationand hydration. To address all the issuesoutlined in this article, the model hasrecently been extended to now simulatetwo-dimensional. When appropriatelyverified, existing uncertainties andmisunderstandings about the in situbehaviour of cemented backfill can thenbe investigated, appropriate simplifiedanalysis techniques can be developed and

used appropriately, and managementstrategies can be provided to operators.

Other benefits of approaching minebackfill from this fundamental point ofview are that it provides the opportunityto investigate the impact of usingalternative binders, plasticisers and anyother additives on the large-scale issuesfaced by operators. In conjunction withmodel development, an experimentalprogram is currently underway to clearlydefine the fundamental differences thatarise from these types of additives.Theseproperties will then be input into themodel to assess their overall impact onthe desired behaviour.

Article references are available on request.

WASM static and backfill testing frameBy Ellen Morton, masters student,WA School of Mines, Curtin University

As part of theongoing

commitment to ground support inAustralia, the Western Australian Schoolof Mines (WASM) has recently designedand commissioned a new and innovativetesting frame based in Kalgoorlie. Thenew facility has been designed to test thestatic response of large scale groundsupport panels and to test large scalebackfill samples.

Funding for the facility was provided byWASM and CRC mining. A minorsponsorship was also received fromDegussa and is greatly acknowledged.

Static ground support testingThe WASM static testing facility iscomplementary to the existing, awardwinning, dynamic testing facility. The newfacility will provide data on currentground support systems prior to dynamictesting conducted at the existing facility.The new static facility (Figure 1)comprises of a steel frame, a clampingframe and five load displacementtransducers. A mechanical displacementcontrolled loading mechanism has been

designed to allow for greaterdisplacements and accurate measuredloading rates.

The facility is capable of testing shotcrete,mesh and spray-on liners with specimendimensions ranging up to 1.6 m x 1.6 m inarea. The deformation rate will be set to4 mm per minute as per ASTM C1550 – 04.The total central deformation will bemeasured to over 350 mm. The loadcapacity of the system is set to 50 tonnes.The new testing facility has developed toconform to the requirements for rounddeterminate panels (ASTM C1550 – 04)for shotcrete testing.

BackfillAs mining proceeds to greater depths(and hence higher stresses) in WesternAustralia, many mines are consideringextraction methods and sequences thatincorporate backfill as an integral part ofthe mining system. In some cases, entryunder or alongside the fill may berequired to enable the full extraction ofthe orebody. To ensure the safety ofoperators working under fill, the physicalproperties of the fill must be known.

The new WASM testing facility will allow adetermination of unconfined compressivestrength of large-scale samples where thespecimen diameter will be much largerthan the maximum particle size. It isenvisaged that specimens 600 mm indiameter and 1200 mm high will betested. Triaxial testing is also beingconsidered for the future.

For more information, please contactErnesto Villaescusa([email protected]) or EllenMorton ([email protected]).

Figure 1 WASM’s new testing facility.


IntroductionMining has occurred in Western Australiafor more than 150 years, resulting inmany thousands of workings that wereabandoned after exploration or mining(Figure 1). Until recently, few of theseworkings and other associated mine sitefeatures were documented.

The Western Australian State governmenthas resourced the Department ofIndustry and Resources (DoIR) tocompile an inventory of the abandonedmine sites for the State. The GeologicalSurvey of Western Australia (GSWA)commenced the inventory in 1999, withthe following objectives:

• to accurately locate and documentabandoned mine sites,

• to document factors relevant to thepublic safety and environmental hazardsthey pose,

• to assess their state of preservation,and

• to quantify the aggregate risk associatedwith each site.

This inventory is intended to provide asound basis for future planning of thenecessary action and rehabilitation athigh-risk abandoned mine sites.

The data within this document aresourced from a comprehensive documentby Ormsby,W.R., Howard, H.M. andEaton, N.W., 2003, Inventory ofabandoned mine sites: progress 1999-2002. GSWA, Record 2003/9.

The inventory principally consists ofindividual mining-related features such asshafts, dumps and buildings that arecommonly found at sites of historic mineproduction. Most of these sites have beennon-operational since 1990 and aretherefore considered to be abandoned.The principal clients of the inventoryinclude the mining industry, localgovernments,WA Department ofConservation and Land Management, landleaseholders, Heritage Council of WesternAustralia, and the public.

A customised database was developedfor the project, and to date a variety ofhand-held personal computers have beenutilised for data capture using both theDifferential Global Positioning System(DGPS) and GPS for accurate locations.Both the database and the applicationhave improved with increased experienceand improved technology.

MethodologyDoIR’s mines and mineral depositsinformation database (MINEDEX)contains all pre 1985 Historic Mine (MH)production sites for Western Australia.Work for the inventory of abandonedmine sites project was prioritised mainlyon the proximity of MH sites to townsand main roads, reflecting the major safetyobjective of the project. High priority siteswere defined as being within 10 km ofmajor towns, 1 km of main roads andselected tourist routes, and within 5 kmof smaller towns and communities.

A number of data sources assisted in theidentification of abandoned mines ortarget areas for fieldwork in any givenarea. The most widely used tool wasaerial photography, but other sources ofinformation included historical maps,geological maps, historic tenementboundaries, data provided by miningcompanies, and orthophotography.

A purpose-made database was developedfor the project, and an application wasinitially designed using Visual CE andMapPad software. Cassiopeia hand-heldpersonal computers were selected fordata capture using the DGPS for accuratelocations.

Figure 1 Abandoned mine workings in Western Australia

Field inventory of abandoned mine sites in Western Australia

By Colin Strickland and Warren Ormsby, senior geologists, Geological Survey of Western Australia


Major improvements were made in mid2002 with the acquisition of SymbolPPT2800 hand-held PCs and theLinksPoint clip-on GPS. The Symbol isdesigned to resist water and rough usage,and has a daylight viewable colour screen.The Symbol’s colour screen enabledmore flexibility in the display of pointdata. The display can be set at a fixedscale, and zoomed in or out with the useof toggle switches. Nevertheless, powermanagement became an important issueduring extended field operation, due tothe power demands of the colour screenand the attached GPS. An externalrechargeable lead-acid battery pack wasupgraded in 2005 with the clip-on 2xrB5700 GPS receiver and lithium-ionbattery pack which enabled 10 hourscontinuous data collection.

The utilisation of ESRI ArcPad 6 GISsoftware under Windows 2002 enabledmodifications to the application, resulting ina several-fold improvement in the range ofdata collected, together with an increaseddata collection rate. Data are output as adbf file and four ArcView shape files.Typing of comments into the Notes andMine Notes fields of the database issimplified by the word recognitioncapabilities of the hand-held device.

The database itself was changed from theMicrosoft Access 97 (MS Access)-basedsystem to the Oracle system, and integratedwith GSWA’s Western Australian fieldobservation database (WAROX). Digitalphotographs of selected feature types werecollected from the outset. The use ofphotographs has subsequently expanded toprovide more useful information. Thephotograph database is now fully integratedwith WAROX.

Extensive database validation is routinelyundertaken, and protocols have beenestablished for the validation of new dataand the extraction of data for clients andstakeholders. Each team memberoperates autonomously, but generallywithin the same region as the others forsafety purposes. In addition, an EPIRBemergency satellite locator beacon isalways carried, and, since 2002, aGlobalstar dual mode GSM/satellitephone is carried to supplement normalGSWA safety procedures.

Spatial information sourcesA combination of spatial information isused for planning, navigation, and targetingpurposes in the office and in the field.Aerial photography was initially the maintool in combination with the MINEDEXMH sites, and historic geological maps,with spatial data provided by miningcompanies augmenting this approach.TENGRAPH plots of topography, MHsites, current mines, and mineraltenements were used routinely during thefirst three years. In 2002,orthophotography, digital historictenement data and digital geological mapswere sourced as valuable tools. Theadvent of the Symbol PC with LinksPointGPS made in-field use oforthophotography and other imagespossible. Furthermore, flexibility withdisplay point symbols and coloursfacilitated the use of multiple targetingdata in the field.

Locations for completed MINEDEX MH sites in WA

Current edition of the "Inventory of abandoned mine sites: Progress 1995 – 2005 DVD


MINEDEXThe MINEDEX database was establishedby DoIR in 1985, and contains records ofthe locations and estimated mineralresources and ore reserves of mines andmineral deposits in Western Australia.The MINEDEX MH sites are the startingpoint for the prioritisation and planning ofabandoned mine site field inspections, andare useful for measuring overall progress.Fieldwork has shown that each site mayrepresent anything from a single shaftthrough to tens of individual mineworkings and associated mine features.

The digital MH site data are viewed usingArcView GIS software on laptops in theoffice and in the field camp. They can alsobe loaded onto the hand-held computerscarried in the field and used as anavigational aid to assist in locating areasof abandoned mine-related features.

There are 11,411 Historic Mine sites(MH) in the MINEDEX database (Figure2), and 4,995 of these (44%) arecategorised as a high priority for field datacollection. As of 31st December 2005 atotal of 5,120 MH sites had beencompleted (76% of high priority sites),with 163,364 mine site features mappedin the field, illustrated with a total of41,961 digital photographs.

WABMINES applicationThe application form is displayed oncethe point is acquired using ArcPad, theuser then records the appropriateattributes of the feature. Originally withthe Cassiopeia PC there was a significanttime delay between acquiring the pointand the display of the application form.This time delay increased as the numberof records increased, and ultimatelybecame a limiting factor to the number ofsites that could be recorded in a day. No

time delay is experienced using theSymbol PC system. All dimensions areestimated, or measured fromorthophotography for larger features, andthe required attributes recorded by styluson the touch-screen keypad. Orientationmeasurements where required are madeusing a compass. Detailed comments aretyped into the Notes and Mine Notesfields of the database, assisted by theword recognition capabilities of theSymbol.

Digital photographsDigital photographs are currently taken.Prior to the 2002 field season, onephotograph was normally taken for allfeatures more than 2 m deep, and mostof these photographs were of shaftcollars. In 2002, a new standard of twophotographs per shaft was adopted.One photograph was taken a moderatedistance away from the feature tohighlight its visibility, and the other was aclose up of the shaft collar. No limits areplaced on the number of photographs,and they can be taken to illustrate anyaspect of any feature. The uniquephotograph number is created in Oraclefor each of the current 41,961photographs stored in the database.

Data managementCurrently data are downloaded daily fromthe Symbol PC to a field-based laptop.This data download is rapid, with the dbffile and shapefiles copied to the laptopcomputer using ActiveSync and MSExplorer. The dbf file is imported into MSAccess, validated, and appended to anindividual master file. Following validationor editing, the dbf file can be exportedand loaded as a new table in ArcMap forviewing the data as an event theme.ActiveSync and MS Explorer are also used

to copy a blank application table, and anyother required data layers, back into theSymbol PC.

ConclusionThe use of innovative technology andapproaches has made the WABMINESproject a success in meeting its goals ofeffective and accurate field data collection.The team is now well positioned tocontinue capturing abandoned mine sitefeatures throughout the State, and toprovide annual releases of the data onDVD, including thumbnails of all digitalphotographs, and an increasing number ofGSWA Bulletins and accompanyinggeoreferenced historical maps. The latestedition of the ‘Inventory of abandonedmine sites: Progress 1999-2005’ wasreleased in February 2006 (Figure 3).

AcknowledgementsColin Strickland and Warren Ormsbygratefully acknowledge the assistance oftheir colleagues within the abandonedmine sites project during the preparationof this paper. This paper is published withthe permission of the Director, GeologicalSurvey of Western Australia.

Seeking to Formalise Your Work Experience and ExpandYour Career Opportunities?

Then come join the ACG team!

We are seeking another PhD student to

participate in Phase Three of the Mine Seismicity

and Rockburst Risk Management Project.

Previous students were involved in practical

applied research and enjoyed the opportunity to

attend conferences and collect data overseas in

Canada and South Africa.

If you are considering postgraduate studies in

mining rock mechanics and are an Australian

resident please contact the ACG to find out more.

Contact Dan Heal – [email protected]

Unable to attend the ACG’s continuing education courses and seminars?Need to expand your understanding of geomechanics in the workplace?

Keep abreast of the latest geotechnical advances by accessing ACG research reports, training products and course proceedingsFrom January to April 2006, more than XX ACG publications and training products have been purchased by local and international mining

personnel.This indicates that industry continues to demonstrate its confidence in the quality of education courses and collaborativeresearch projects undertaken by the Centre.To find out why industry turns to the Centre as the main source of geomechanical knowledge,

contact the ACG for a detailed list of seminar proceedings, training tools and research reports.


Hosted by the ACG and the Centre forLand Rehabilitation (UWA) this is the firsttime that a range of targetted mineclosure issues will be explored in aninternational forum.

One of the greatest challenges facing theglobal mining industry is the issue ofeconomic and socially acceptable closureof mine sites. The increasing attentionbeing paid by the media to the legacy ofabandoned mine sites has focused publicinterest on mine closure issues. Inresponse, legislators and regulators areimplementing various financial instrumentsto provide surety that closure will beaffordable. These are often underpinnedby various rehabilitation criteria that mustbe met to avoid financial penalties. Anexample is the environmentalperformance bond requirement inWestern Australia, which is imposed toensure that the state is not exposed tounacceptable costs should mine operatorsfail to meet the rehabilitationrequirements of their lease. For tailingsstorage facilities, for example, the amountof the bond is AUD$12,000 per hectare.

Planning for land rehabilitation and siteclosure from an early stage of a miningoperation is an important way ofdecreasing the cost of the process.

It is also important to have clearly defined,unambiguous and appropriate criteria forwhat constitutes acceptable closure.Approval for future mining projects willmore likely be obtained if the industrydemonstrates it is able to close existingsites in a responsible and environmentallyand socially acceptable manner.

The organisers are delighted that theworld-first seminar will be held inAustralia. It is hoped that the event willinitiate an annual vehicle for legislators,mine owners and operators, consultants,service providers and researchers fromthroughout the world to exchange viewson how best to ensure that future closureof mine sites is achieved at minimum cost,whilst ensuring that future environmentaland social impacts are minimised. By usingopportunities such as this for setting theagenda for future research andoperational directions, the viability ofmining operations can be ensured.

The technical program will includecomprehensive and highly relevanttechnical papers emphasising innovationsand application of state-of-the-arttechnologies and closure strategies fromaround the world. More than 50 papersfrom leading local and international mineclosure practitioners and strategists areexpected to be presented at this unique,world-first mining event.

Major Sponsors

Rehabilitation is a critical component of the miningcycle

One of the greatest challenges facing industry is the socially acceptable closure of mine sites

Mine Closure 2006 comes to townThe widespread challenges of closing mines in an environmentally and socially acceptable

way will be addressed by the international mining community at the First International

Seminar on Mine Closure planned for Perth,Western Australia in September 2006.

GHD LOGO STILL UNABLETO BE READ

Visit www.mineclosure.2006.orgfor more information.


IntroductionCorrosion of barrel and wedge anchorsand the consequences for the entire cablebolt performance is poorly understood.Recent developments in cable bolt designhave meant an increased reliance onanchors to be serviceable for long periodsof time, especially for applications wherethe strand is decoupled from the cementgrout. In particular, yielding bolts arecustomised in the toe and collar region.

Anchor failures after short time durationsand under low loads have been observed inseveral underground mines in the EasternGoldfields of Western Australia. Failure isoften characterised by the barrel andwedge remaining intact after being found onthe floors of drives with no evidence ofstrand rupture (Thompson, 2004).

These failures are attributed to installationpractices and corrosion. The corrosion ofbarrel and wedge anchors is intrinsicallylinked to the environment in which theyare installed. Circumstances where groundwater is flowing or dripping over theexposed end of the reinforcement areconsiderably more corrosive than dryenvironments. However, corrosion in suchinstances is highly variable and difficult topredict accurately.

In an attempt to better understand thebehaviour of cable bolt anchors, variousbarrel and wedge anchor configurationswere placed within a corrosion chamber tosimulate underground environmental

conditions. Laboratory pull tests were usedto determine the force-displacementresponse and the influence corrosion hason the load bearing capacity of the anchors.

Laboratory testingTwo basic barrel and wedge anchorconfigurations are presently used within themining industry. These anchors incorporateeither a flat ended barrel or ahemispherical ended barrel to be used witheither a two-part or three-part wedge. Inthe tests described in this investigation,two-part wedges were used with the flatended barrel and three-part wedges withthe hemispherical based barrels.

Two different strand types were alsoexamined. The standard plain strand andthe deformed compact strand, which isincorporated with the yielding cable boltunder examination.

A number of corrosion protectionmethods were trialled. The methodsincluded galvanising of the barrel andthree simple and commonly found barriercorrosion inhibitors such as grease,bitumen and wax. Some tests wereconducted with galvanised strand. Themajor focus of the testing was todetermine the effectiveness of the variouscorrosion protection methods for thehemispherical barrel and three-partwedge used with compact strand.

Figure 1 is a schematic long-sectionrepresentation of the testing system used.Following a grout curing time of 7 days,

the plate and barreland wedge wereinstalled and thesystem loaded to 8tonnes (~80 kN)using a hydraulic jack.Corrosion inhibitors

were then applied to

the appropriate samples. The majority ofsamples were placed in the WesternAustralian School of Mines (WASM)corrosion chambers with the remainderbeing tested to provide a non-corrodedreference test.

Simulated underground environmentThe everchanging nature of a workingmine continually modifies the localenvironmental conditions. It is thereforeimpossible to maintain consistentenvironmental conditions for theextended periods of time necessary tostudy the processes and rates ofcorrosion for different reinforcementmaterials. To overcome this, corrosionchambers were designed and developedat the WASM to simulate the corrosiveenvironment of underground mines.

The chambers maintain a constanttemperature and humidity by use of anelectronic sensor system independent ofeach chamber. Ground water wascollected directly from the rockmass andtransported to the corrosion chambers.An electronic pump is used to pump thewater through purpose built reticulationproviding a constant supply of drippingground water onto the reinforcement andsupport being tested (see Figure 2).The water condition is monitored and thewater is changed when the conditionsdepart from the underground situation.

The average temperature and relativehumidity were maintained at 30°C and90% respectively. The near neutral pHground water is hyper saline with highconcentrations of chloride and sulphideions. The presence of these ions makessteel more susceptible to pittingcorrosion. The extremely high TotalDissolved Solids (TDS ~230,000ppm)and moderate temperature have the

Testing and evaluation of corrosion on cable boltanchors

By Rhett Hassell, PhD student, Ernesto Villaescusa, professor of mining rock mechanics,and Alan Thompson, senior research fellow, CRC Mining,WA School of Mines, Curtin University

Figure 1 Schematic representation of split pipe testing system


effect of reducing the dissolved oxygencontent. This can reduce the corrosivityby limiting the amount of oxygen availableto the electrochemical corrosion process.

Testing of the barrel and wedge anchorsTesting of the various barrel and wedgeanchors was conducted immediately afterinitial anchor installation and at 3, 7 and10 months of exposure to the conditionsin the corrosion chambers. Testinginvolved subjecting the samples to tensionloading to a maximum of 200 kN,provided by the hydraulic Avery machinelocated in the Rock MechanicsLaboratory at WASM. Three tests wereconduced for each of the combinations.

Results of laboratory testing

Hemispherical barrel and three-partwedge with compact strandThe anchor configuration experiencedfailure in two of the three samples after 7 months and one sample after 10 months.Failure occurred at the wedge/strandinterface with the strand pulling throughthe anchor and was associated with smallwedge movement relative to the barrel.Failure took place at loads ranging from 22 kN to 111 kN that are significantly lowerthan the strand force capacity of 250 kN.

The internal section of the failed barreland wedge anchor shown in Figure 3displayed a build up of corrosion productson the internal surface of the barreltogether with shearing of the wedgeteeth. Anchors that perform properlydisplayed notably less corrosionaccumulation (see Figure 4).

The absence of corrosion products on thenon-failed samples strongly suggests that

corrosion is responsible for failure.Corrosion products on the internalsurface of the barrel increase the frictionalresistance at the barrel/wedge interfaceand this prevents sliding of the wedgerelative to the barrel. This in turn preventsthe wedge from gripping the strand.

Barrier corrosion inhibitorsAnchors that were coated with grease,wax or bitumen had significantly fewerinstances of failure. Of the three inhibitorsused, only the grease coated anchor failedonce after 10 months. Examination of thesample following testing indicated muchhigher levels of corrosion on the internalbarrel surface than the non-failedcounterparts.

The bitumen coating performed best atpreventing corrosion occurring over theentire anchor. Specifically, corrosion on thecritical internal barrel/external wedgesurface was inhibited.

Hemispherical barrel and three-partwedge with black and galvanisedplain strandThere was no failure of the barrel andwedge anchors used with either plainstrand or galvanised plain strand. Lowlevels of internal corrosion wereobserved. When compared with thecompact strand it appears that themodified geometry of the strand doesnot allow for a “tight” fit, allowing forhigher levels of corrosion.

Galvanised hemispherical barrel andthree-part wedge with plain strandThe anchor consists of the barrelgalvanised to a thickness of 75 µm withthe three-part wedge remaininguncoated. The galvanised anchorperformed extremely poorly in thetesting, with failure of one sample in the 3 month test and failure of all samples inthe 7 and 10 month tests at very lowloads (less than 50 kN). Inspection of theanchors revealed that steel corrosion ofthe anchor was low but oxidising of thegalvanising was noted by the presence ofzinc carbonate on the barrel surface.

The effectiveness of zinc galvanising toprotect steel from corrosion is wellknown and documented. However, zincmetal is considerably softer and providesa rougher surface than the steel it coats.

This has the effect of increasing the frictionat the barrel/wedge interface due to thesteel wedge digging into the galvanising.This prevents wedge movement andsubsequently leads to shearing of thewedge teeth and strand slippage. Itappears minor levels of zinc corrosion mayfurther increase the problem.

Flat barrel and two-part wedgeThere was no failure of the anchors thatused two-part wedges for either thecompact or plain strand. This may notalways be the case. Previously reportedtest results showed that anchors withtwo-part wedges failed by slipping relativeto the strand after 6 months of exposureto mildly corrosive environments(Thompson, 2004).

Impact of wedge movementThe long-term performance of a cablebolt anchor in a corrosive environment iscontrolled by the frictional resistancebetween the internal surface of the barreland the outside of the wedge. Corrosionand galvanising of this surface increase thefrictional resistance restricting wedge slipand minimising gripping of the strand,which leads ultimately to prematureanchor failure, often at low loads.

Another factor that influences the abilityof the wedge to slide relative to thebarrel is the inherent roughness of thecontacting surfaces. The smoothness ofthe inner surface of the barrel and the

Figure 2 Corrosion chamber displaying barrel andwedge testing at rear

Figure 3 Internal condition of failed barrel andthree-part wedge anchor. Note the corrosion on thebarrel surface and the shearing of the wedge teeth

Figure 4 Internal condition of barrel and three-partwedge anchor that did not fail after 10 months incorrosion chamber


outer surface of the wedge vary betweenbatches from the different suppliers. Insome instances, the roughness frommachining is clearly visible and easily feltby running one’s finger over the surfaces.

Figure 5 summarises the measured wedgemovements for each of the 10 monthtests. Anchor failure can clearly be seen tocorrelate with minimal wedge movement.

Summary and conclusionsThe current anchor assembly employedwith a commercially available yielding cablebolt has a predicted anchor life of less than7 months in a hyper saline ground wateraffected environment. The service life canbe extended to greater than 10 months by

the application of simple barrier corrosioninhibitors such as bitumen.

The anchors with two-part wedgesdemonstrate a greater resistance tocorrosion than those with three-partwedges. In addition, they also showed astiffer response when load is applied. Thetwo-part wedges have fewer pathways forthe ground water to infiltrate the internalsection of the barrel, as well as having acloser fit at the barrel/wedge interface.

Those anchors tested in combination withplain strand display less corrosion on theinternal section of the anchor than theanchors used with compact strand. Themodified geometry of the compact strandappears to allow for greater corrosion to

occur. This was observed with both thethree- and two-part wedges.

Experience from this testing has shownthat the external condition of the barreldoes not give a conclusive indication tothe amount of internal corrosion of theanchor. Therefore, a visual assessmentsystem cannot be used to determine theextent in which corrosion is influencingthe capacity of an anchor.

Finally, and most importantly, it is critical inservice that the ability of the wedge toslide relative to the barrel is maintainedso that more tension can develop in thereinforcement to resist rock movement.Galvanising of the anchor is notrecommended due to the soft zincgalvanising coating increasing the slidingresistance at the barrel/wedge interface.This prevents the barrel and wedgeanchor from being effective. It is thereforestrongly recommended that a high qualityand long-lived lubricant is placed at thebarrel/wedge interface during installationto provide a low friction interface thatalso assists in corrosion protection.

AcknowledgementsThe authors acknowledge the support ofGoldfields Australia, St Ives Operations inthe implementation of this work.The authors also wish to recognise thesupport of the Minerals Institute ofWestern Australia (MERIWA), BHPBilliton Ltd, Placer Dome Asia Pacific,Barrick Gold Australia, Degussa, StrataControl Systems and AVKO Drilling.

Article references are available on request.

Table 1 Summary of test results

Barrel and Wedge Anchor Combination Initial Failure

Age (months)

Failure Mode Failure Load (kN)

Anchor Strand Coating Min Max

Hemispherical 3-part compact none 7 Wedge/strand slip 22 111

Hemispherical 3-part compact grease 10 Wedge/strand slip 27 27

.Hemispherical 3-part compact bitumen No failure

Hemispherical 3-part compact wax No failure

Hemispherical 3-part plain none No failure

Hemispherical 3-part galvanised plain none No failure

Hemispherical 3-part plain galvanised 3 Wedge/strand slip 21 47

Flat 2-part compact none No failure

Flat 2-part plain none No failure

Figure 5 Total wedge movement of anchors after 10 months in the corrosion chamber


The ACG research project “HighResolution Seismic Monitoring in OpenPit Mines” commenced in 2005 and seeksto explore and further understand thecomplex nature of slope movement inactive Australian open pit operations.With industry backing, the project aims toprovide a better tool to minimise thefinancial and safety risks associated withpotential slope failures by the earlydetection and analysis of the microseismicwarning emitted by the failing rock.

The project has moved into its nextphase, with the installation of two moretrial arrays at BHP Billiton Nickel West’sMt Keith operation in addition to anexisting array (see Figure 1). These threearrays will be monitored over the nextfew months after which a decision will bemade as to what trial site will beupgraded to a full 16-sensor system,based on recorded seismic activity.

From March to September 2005, a totalof 270 seismic events were recorded bythe ESG Paladin system at the 319 trialsite (see Figure 2).The activity rate is bestdepicted in a Magnitude-Time plot asshown in Figure 3. Changes in the activityrate can be correlated with significantexternal events, for example, a rainfallevent corresponded to a significantchange in the slope of the curve.

Preliminary data analysis suggests that theseismicity is dominated by volumetric ordilatational deformation, as opposed tofault-slip. This could imply that rockmass

deformation at this site is characterisedby intact rock failure rather than slip ondiscrete structures.

Preliminary numerical modelling studies

highlight a spatial correlation betweenone of the identified clusters and a zoneof volumetric strain change (see Figures4a and 4b). This finding further suggeststhat the seismic deformation is related topit geometry and mining induced stresschanges.

At Xstrata Zinc’s Black Star open cut(Mount Isa), the sensor array design hasbeen finalised (see Figure 5) and the ISSsystem hardware is ready for installation.

The Black Star system offers theopportunity to study the interactionbetween pre-existing undergroundcavities and the developing pit.

This ACG research project aims to deliversolutions that could become critical tothe success of Australian and global deepopen pit operations.The direct benefits ofenhanced slope monitoring capabilitieswill be a more progressive slope designand a diminished risk of failure.The earlydetection of slope movement will alsoallow for a tactical response to avoid ormanage loss of slopes.

AcknowledgementsThe significant contributions made by theproject sponsors, BHP Billiton NickelWest, Xstrata Zinc and the Minerals andEnergy Research Institute of WA, bothtowards project justification and funding,and the efforts of the site personnel, aregreatly appreciated.

For more information about HighResolution Seismic Monitoring in OpenPit Mines, please contact Gordon [email protected].

What’s shakin’ your pit?By Gordon Sweby, project leader,Australian Centre for Geomechanics

Figure 1 Location of trial arrays at Mt Keith open pit

1 km

N

Site 319

Figure 2 Total events recorded over the monitoringperiod, scaled to Moment Magnitude and withsignificant clusters highlighted

300m

N

Figure 5 Planned seismic array at Xstrata Zinc’sBlack Star open cut.The planned pit geometry inrelation to the known subsurface cavities is asshown

300m

N

Figure 3 Magnitude-Time plot showing activity rateover the monitoring period. A change in slope of theactivity rate curve corresponds with a high rainfallevent

Figure 4a Oblique view of a best-fit plane throughseismic cluster, showing contours of cumulativeseismic potency

Figure 4b Alignment of best-fit plane with local pitgeometry


IntroductionTwo falls of ground in one developmentheading at Ballarat East mine andincreasingly weathered ground conditionshad the mine’s technical staff searching forsmart mining solutions.

The vent access drive was designed toconnect the mine’s development to thebase of the exhaust shaft. As the shaftwas being excavated as a conventionalshaft sink, the vent access was designed asan incline through slightly and moderatelyweathered ground conditions. Theprimary reason for mining the access asan incline was to reduce the shaft sinkdepth and decrease the scheduled timeto breakthrough. Breakthrough into theshaft was considered a critical path forramping up production at Ballarat East.

The initial fall of ground was within the first20 m of the vent access. The heading waspassing through a 45º west dipping faultwhen it began to self mine. The second fallof ground occurred another 50 m alongthe drive when a second fault was being

cut across. This fault differed to the first,being a sub-vertical cross course fault.

With two failures and no reason to thinkthere would not be more with aconventional mining approach it was timeto do something drastic. Recovering fallsof ground was delaying the miningschedule and increasing developmentcosts. As Einstein once stated, “Insanity isdoing the same thing over and over againand expecting different results.” Thecurrent methods of spiling through the

faults and reducing the cut lengths wereno longer working; a new pre-supportmethod was required for these faultconditions in moderately to highlyweathered rock.

Ballarat East geological andgeotechnical characteristicsBallarat East is situated entirely within

Lower Ordovician cyclic sandstones,

siltstones and mudstones that have been

weakly metamorphosed and tightly folded

about north-south trending axes. The

interbedded sediments are intensely

weathered to a depth of at least 100 m

below surface; these rocks are typically

very weak with unconfined compressive

strengths of less than 5 MPa.

Below this depth the weathering

decreases and the strength of the rock

increases. However, extremely weathered

rock can persist to around 300 m below

surface, typically controlled by structural

features.

The 45º west dipping faults are spaced

from 5 to 70 m apart striking

approximately north-south. The faults are

identified by quartz veining and associated

carbonate veining, arsenopyrite alteration

and rotated cleavage. Fault thicknesses

range from 1-10 cm, with veining around

the fault extending over 10 m away from

the fault in the form of tension veins.

Around the intersection of these 45º

west dipping faults and fold axes or

and/or stratigraphic units the Ballarat East

mineralisation is found.

The cross course faults at Ballarat East

are large fault structures that cross cut

the stratigraphy at regular intervals. These

faults are typically sub-vertical and are

identifiable by their puggy clay brecciated

appearance and chloritic alteration. The

faults typically do not rotate the bedding

and the cross cutting faults tend to be

more oxidised than other structures. The

faults can be up to 40 cm thick with a

zone of broken and weathered rock

surrounding the fault from 1 – 20 m

wide. The weathering halo decreases

with depth, and from around 300 m

below surface is insignificant. These fault

structures can exhibit up to 50 m of

lateral offset along the fault.

Where the weathering halo occurs the

rockmass is extremely broken

(RQD = 0), the rock strength is

significantly decreased and the ground

conditions go from poor ground to

extremely poor ground. This rockmass is

then not self supporting in a 5 m x 5 m

development heading and typically

unravels in the first hour after firing.

Geotechnical probe drillingThe geological structural models used at

Ballarat East were extrapolated from

mapping of the historical underground

workings and then projected across the

Ballarat East mining area. Cross course

faults are not linear features and the

projected models were in many cases up

to 50 m out. When mining through these

zones it is critical to know the exact

position and width of the fault to ensure

that the correct support is used going

into and through the fault.

Geotechnical drilling in front of the

decline became vital for determining both

the location and width of these faults.

It was important that the drilling followed

Pressure grouting – the end of insanityBy Kate Williams, senior geotechnical engineer, Ballarat Goldfields NL

Blocker grouting at the face

Drill rig set-up in IT basket


the exact line of the development as the

faults tended to change characteristics

along strike. In other areas of the mine

where the same faults were developed

through, the faults exhibited different

characteristics even when the drives were

only 20 m apart.

Geotechnical probe drilling along thelength of the vent access indicated thatanother four cross course faults were tobe intersected before breaking throughinto the shaft. Ground conditions wereexpected to deteriorate as the driveinclined into the more weathered rock.

Pressure groutingIt was at this stage that pressure groutingwas suggested as a possible solution. Thismet with the usual “that’s too expensiveto use in a mine” and “that’s not used inhard rock metalliferous mines”. We wereslowly coming to the realisation that therock was not hard, especially around theweathered faults where it moreresembled clay.

The next fault along the drive had a 20 mwide weathering halo according to thegeotechnical probe drilling. It was at thisstage grouting expert Bruce Grant,Mulitgrout Australia, was called in todetermine if pressure grouting wasapplicable in the faulted groundconditions at Ballarat East – it was.

Initial pressure grouting trialThis began our foray into the world ofpressure grouting. Based on the size andlocation of the fault, a pattern of holeswas designed that would consolidate theground around the designed drive profile,concentrating on the areas of shoulders,backs and upper part of the face.

Drilling was undertaken using the onsiteproduction drill rig with the maximumhole length at 20 m. It took three shifts tobore the holes then three shifts to grout.

The grouting system utilised was a speciallydeveloped system,“MultiGrout®”,developed out of civil tunnelling practicesin Norway. An ultrafine cement productwas used with the maximum particle size<15µm giving improved penetration intofine cracks. A product called GroutAid®was used as a stabiliser, Groutaid® is aspecially processed microsilica based slurryand it allows extremely “thin” or wet groutsto be injected without problems withbleeding and fluid loss. This slurry adds alarge number of extremely fine sphericalparticles of high specific surface area.When this high surface area is incorporatedwith the high internal attraction forces, thecement and microsilica particles remainsuspended without settling. This meansthat high water cement ratios can beachieved with enhanced grout flow andpenetration properties.

Each of the drillholes were packed closeto the collar using mostly mechanicalpackers. The occasional hole required ahydraulic packer because the drilling hadenlarged the hole collars. Grouting beganin the holes at the centre of the face andslowly worked up into the shoulder holesand then onto the back holes. As eachhole was grouted, grout connections toother holes were carefully managed toensure each grout hole was kept “alive”and that each hole was pressurised.Because of the blast damaged rock withinthe first metre at the face, it was difficult

to control grout leakage from the face.Despite the face condition, maximumpressures achieved were around 4000 kPa(40 bar). Grout usage was around 2.5 timesthe hole volume; whilst large amounts of grout were not required for joint/voidfilling, the high pressure injection squeezed and consolidated the clay richweathered rock.

Mining commenced two shifts aftergrouting completed. Previous experiencewith self mining headings dictated acautious approach to development.Grouted rebar was still being installed asspiling and cut lengths were shortenedfrom 3 m to 1.5 m. Improvements in theground conditions were visible even inthe first cut. Comments from theoperations team were that this was thebest ground that had been mined in thedrive so far. Drilling had shown this wasthe worst ground encountered thus far.Conditions had improved so much that itwas decided half way through the treatedzone to increase cut lengths from 1.5 mto 2 m. All was going fine until the groutcurtain was exceeded. The first cut intothe untreated ground unravelled. Thisgave the final conviction that the pressuregrouting had worked.

Second pressure grouting trialSubsequently, two more sections of thisdrive (an additional 73 m) were treatedwith pressure grouting, though instead ofspilling in the development cycle, spilingbars were installed above the drive profileand pressure grouted through.

Iain McPhedran, Eastern Mining Services,worked on the first pressure grouting trial

Ground conditions at Ballarat East are constantlychallenging the geotechnical team

Grout trial one grout holes Grout trial two spiling and fault locations


and suggested a process that he wasusing in underground coal mines. Itinvolved pressure grouting throughpreinstalled spiling bars developedspecially for this type of work. The spilingbars were pushed into a predrilled holeby a small air rig. Eastern Mining Servicesadopted their current drilling equipmentto fit inside an IT basket so that drillingcould take place as close to the backs ofthe drive as possible. This created agrouted canopy to mine beneath,significantly reducing the risk of a failurewithin the drive. It also removed therequirement for spiling duringdevelopment, greatly decreasing themining cycle time. Where the spiling barssat within the drive profile the bars weremade of polypipe and when they satabove the drive profile the bars weremanufactured from steel.

These holes were not sealed withpackers, breather valves were groutedinto the collar of each hole and then the

grout was pumped through the spiletubes in the same manner as the initialtrial. Pressures of around 4000 kPa wereachieved once again.

Another improvement on the initial trialwas to seal the blast damaged rock at theface by drilling short holes into the face(7 m long) and then injecting a fast settinggrout into this zone. The spilling backholes were then drilled through this shortpre-grouted zone. This allowed thepressures to be built up behind the initialblocker grout zone.

Once again the improvements in therockmass were noticeable with previouslydifficult mining conditions becomingmanageable.

ConclusionThe experience at Ballarat East illustratedthe importance of looking for solutionsoutside of our industry. The groundconditions at Ballarat East are constantlychallenging and a large variety of supporttechniques are used.

Pressure grouting has allowed mining toprogress in extremely poor groundconditions with little affect on thedevelopment cycle. Previously, miningthrough the faults slowed developmentdown to 1 m/day, with the pressuregrouting this increased to 2 m advanceper day.

Pressure grouting has been successfullytrialled at Ballarat East in extremely poorground conditions and is a ground controlmanagement tool that will be utilisedwhere geotechnical drilling reveals largeweathered fault zones or difficult tomanage ground conditions.

AcknowledgementI thank Bruce Grant from MultiGroutAustralia and Iain McPhedran fromEastern Mining Services for theirassistance in relieving our insanity and toBallarat Goldfields NL for permission topublish this article. For furtherinformation, please contact Kate Williamsat [email protected].

Discussion on Ground Control ManagementPlans Call for Presenters• How do you manage major hazards at your site?

• Do you have risk management systems or strategies that you wouldlike to share?

• An opportunity for operations to share ideas and experiences.

Preliminary ProgramWednesday 31 May – Workshop and EAGCG Meeting

Session 1: Jim Joy University of Queensland and John Moss, NSWDept. of Primary Resources.

Session 2: Case studies, presentations and discussions.

Session 3: EAGCG meeting

Thursday 1 June – Mine Site Visits

To register your intent to present or attend this forum, please contactUday Singh, EAGCG Secretary via [email protected].

EAGCGWorkshop and

TechnicalInspections

“Hazard Identification

& Risk Management for

the Mining Industry”

31 May – 1 June 2006,Broken Hill, NSW


BackgroundHistorically, the largest open pit mines

have been from 300 m to 500 m deep.

In the past 10 years, some open pit mines

have reached up to 800 m deep, and

depths are expected to exceed one

kilometre within another 10 years. The

inadequacy of current slope design in this

inverted 'high rise' environment has been

exposed by a number of slope failures.

These failures have resulted in multiple

fatalities and production losses.

Over the years the slope design processin large open pit mines has beenhampered by critical gaps in ourknowledge and understanding of therelationships between the strength anddeformability of rockmasses and the likelymechanisms of failure. Particularcomplications arise when the rockmassare neither homogenous nor isotropicand low stress regimes encourage largedeformations. We usually manoeuvredaround these difficulties by smearing thewhole system and assigning ‘average’strength properties to the rockmass,calibrating it using existing slopemovement data, and performingparametric studies to isolate what wejudge to be the more unlikely events.Although this is accepted practice, it hassome distinct disadvantages. Notably, byapproximating the behaviour of the wholesystem we may have totally masked acritical variation in the geotechnicalmodel. Additionally, the procedure doesnot overcome the fundamental issue ofaccounting for anisotropy and largedeformations. Last but not least, bycalibrating against a known event we mayin fact be limiting our chances of reliablypredicting a future event.

Collectively, these anomalies havegenerated a need to step outside the boxand reassess the fundamentals ofrockmass strength and slope failuremechanisms from first principles. Withfinancial support from a number ofinternational mining companies withinterests in open pit mining, CSIROExploration & Mining has initiated aresearch project which has this objective.

The project is also supporting parallelstreams that seek to bring into the publicdomain the outcomes of the research,together with all current knowledge aboutgeotechnical data collection andmanipulation, uncertainty analysis, slopestability analysis, and risk management viaupdated pit slope design and riskmanagement guidelines. Existing manualssuch as that produced by CANMET almostthirty years ago remain as valuableliterature references, but the time has comefor a new generation guidelines that detailaccepted practice for today’s practitioners.

Research objectivesResearch in the Large Open Pit project is

examining the attributes that control the

strength of the structured rockmass as it

deforms in the stress environment of a

deep pit and how candidate failure

surfaces may propagate through the

dilating rockmass along the path of least

shear and/or tensional resistance. The

research includes three complimentary

research streams:

1. Preparation and publication of an

authoritative new generation Pit Slope

Design guidelines that links innovative

mining geomechanics research together

with accepted practice. The guidelines

will incorporate a database of pit

design, performance and operational

issues, including topics such as hands-on

and remote data acquisition, rockmass

characterisation, and the

appropriateness of different design

approaches.

2. Research that provides vital new

knowledge and design criteria that

describe the critical gaps in our current

understanding of rockmass failure in

large open pit mine slopes. Research

tasks will be directed at enabling the

effective use of geological and

geotechnical data in assessing rockmass

characteristics, 3D modelling and

simulation of slope failure mechanisms,

design analyses, and uncertainty analysis.

3. Development of practical risk

management criteria focused on the

relationship between risk reduction and

the uncertainties of slope design and

their impact on pushback strategies,

equipment selection, costs and benefits,

and mine performance criteria.

CSIRO researches open pit techniquesBy John Read, research director – Mass Mining projects, CSIRO Exploration and Mining

CSIRO's research seeks to develop new and bettermethods of predicting the relability of rock slopes inlarge open pit mines

A group of 10 mining companies representing the majority of the world’s production of diamonds and base

metals are working with the CSIRO Exploration and Mining to develop new and better methods of predicting

the reliability of rock slopes in large open pit mines.This innovative and timely research project is well

underway and is expected to be completed within the next two years with funding of more than $2.6 million.


OutcomesThe outcomes will be used by theSponsors to set practical slope designcriteria and methods of analyses thatdescribe the reliability of pit walls, helpingto prevent costly failures.

Some open pit mines have reached up to 800 mdeep, and depths are expected to exceed onekilometre within another ten years

Project sponsors

• Anglo American PLC, London,England

• Barrick Gold Corporation,Toronto, Canada

• BHP Billiton Innovation Pty Ltd,Melbourne, Australia

• Corporacion Naciónal Del CobreDe Chile ('Codelco'), Santiago,Chile

• Compania Minera Dona Ines deCollahuasi SCM, Iquique, Chile

• DeBeers Group Services,Johannesburg, South Africa

• Newcrest Mining Ltd,Melbourne, Australia

• Newmont Australia Ltd, Perth,Australia

• Xstrata Queensland Ltd,Brisbane, Australia

• Debswana Diamond Co,Gaborone, Botswana

For more information, pleasevisit www.lop.csiro.au

Following on from the very successful 2006 International Symposium

on the Stability of Rock Slopes in Open Pit Mining and Civil

Engineering Situations hosted by the SAIMM in South Africa last

month, the ACG is delighted to bring this innovative event to

Australia for the first time. Co-Chairs,Yves Potvin, ACG, and John

Read, CSIRO Exploration and Mining, look forward to presenting a

symposium that will explore the significant developments in the

design, analysis and excavation and management of rock slopes.

Slope Stability 2007 will explore the significantdevelopments in the design, analysis, excavationand management of rock slope

2007 INTERNATIONAL SYMPOSIUM

on the Stability of Rock Slopes in Open Pit Mining and Civil Engineering

12 – 14 September 2007, Sheraton Perth Hotel,WA

Symposium objectivesSlope Stability 2007 aims to:

• document information on state-of-the-art rock slope design andexcavation,

• provide a forum for the latestinformation on the application ofprobabilistic and risk analyses ofslopes, and current and new slopemonitoring and maintenancetechniques to be presented andexplored, and

• present relevant and interesting casestudies.

Who should attend the symposium? All open pit personnel, minemanagement, blasting specialists, slopestabilisation and monitoring serviceproviders, road and rail authorities, civilengineers, OH&S personnel, researchers,consulting engineers and contractors.

Topics Papers are invited on any aspectrelevant to rock slopes, including:

• slope failure mechanisms,

• slope design criteria and design methods,

• risk analysis and numerical stressanalysis,

• slope monitoring techniques,

• slope excavation – blasting techniques,

• support and stabilisation of slopes,

• ground water implications,

• financial aspects and slope stability and

• rockfalls – analysis and control.

Key Dates

Submission of abstract26 February 2007

Submission of paper21 May 2007

AusIMM Large Open PitMining Conference10 – 11 September 2007

ACG Sirovision User’sConference – Open Pit andUnderground Applications11 September 2007

ACG Rock Slope StabilitySymposium12 – 14 September 2007

The ACG is also pleased to announce thatthe symposium will be held in conjunctionwith the AusIMM’s well established andhighly regarded Large Open Pit MiningConference. Contact Josephine at theACG for more information.


The skills shortage, effecting mostAustralian mines, has also added a degreeof difficulty in providing the depth ofgeotechnical experience in-house withinCBH to meet these challenges.

The geotechnical challenges at Endeavorwere highlighted by the crown failure ofthe 6z2 stope in October last year. Sincethe collapse, CBH has returned the mineto production. Through an innovativeapproach, Coffey Mining and CBH haveworked together to put in placegeotechnical management strategies toextend the mine’s life.

Under an innovative geotechnical servicesarrangement, the companies have providedthe necessary depth of experience tosupport the Endeavor mine. This alsoprovides mentoring and training to developthe in-house capability of CBH staff.

A long-term relationship such as this hasmutual advantages to both companies. Itenables the full depth of experience ofCoffey Mining experts to be focused onspecific geotechnical problems. Thesespecialists also retain their operationaledge by temporarily filling technicalservices production roles during CBH’srecruitment phase.

By providing this continuity, a seamlessintegration with the CBH technicalservices team is maintained. As well asachieving a high degree of knowledgesharing and transfer between teammembers, the arrangement also allowsCoffey Mining staff to provide sitecoverage enabling CBH staff to work onspecific projects.

Work has commenced to extract the A –East and West pillars from the 6z1 stope.A high level of geotechnical focus wasrequired for mining of this stope due toits relative position with respect to thepreviously failed 6z2 stope.

Integrated services processimplementation

Example – integrated processOne such case of a fully integratedgeotechnical service (i.e. inclusive ofbackfilling consisting of dry fill) was themining of the 6z1 A-pillars (see Figure 1).

The process involved in preventingpotential extensive overbreak around the6z1 stope is outlined below:

• All the geological and geotechnicalhazards (e.g. major regional faultstructures and rockmass conditions)have been assessed on-site. Thisinformation was forwarded to a seniorgeotechnical engineer off-site for reviewand evaluation. This information wascombined with a fully representativerockmass model numerically analysedto determine the stress condition prior,during and after extraction.

• To evaluate and control the potentialfor massive overbreak, anunconsolidated waste fill height withinthe stope above was required to be

maintained at a certain level (seeFigure 2). Maintaining the waste fillheight had other implications in dilutingthe recovered ore, hence theintroduction of proper controls toensure a low risk operation.

• These controls, e.g. modified blast rings,were evaluated and reviewed on-siteduring a senior geotechnical consultantsite visit, which resulted in a finalalternative blast ring design, reduction inblast ring quantity and strategicallyplaced cable bolt design (see Figure 3).

• The necessary controls wereimplemented, (refer to Figure 3 for ringdesign and cable bolt reinforcementand Figure 2 showing a cross sectionindicating fill height maintenance), toensure the risk of extensive overbreakis mitigated and potentially eliminated.

• Feedback on the success of controls(i.e. maintaining fill height) beingimplemented is discussed every day atproduction meetings through areconciliation process of tonnes drawnversus waste tonnes filled.

Endeavor Mine shines with an integrated geotechnical service

By Wouter Hartman, associate geotechnical engineer, Coffey Mining

Consolidated Broken Hill (CBH) Resources is accessing new primary ore sources at their Endeavor Mine in

Cobar, New South Wales. During this development phase the bulk of production is obtained from pillar

extraction. This presents a technically challenging environment, especially considering the backlog of open

voids inherited by CBH from the previous mine operators.

Figure 1 View of 6z1A-Pillars

Figure 2 Cross section lookingWest – South west, showing fillheight to be maintained during6z1 A-Pillars extraction

Figure 3 Plan view of alternative ring design andcable bolt reinforcement for 6z1A-Pillars

revised copies exactly sameas previous


Aspects critical to the success of thisintegrated process, which supportedthe above case, are highlightedbelow:• 3-Dimensional numerical analysis

consisting of block model constructionrepresenting different rock materialproperties experienced at Endeavour,combined with the site geological andgeotechnical information was used inthe detailed assessment to identifypotential overbreak in the 6z1.

• Extracting the A-Pillars of the 6z1 willhave possible stability implications whenextracting the 7z1 crown pillar belowand the introduction of monitoringequipment in the form of SMART cablebolts and SMART “MPBX”extensometers to provide informationregarding rockmass response.

• In order to ensure that other stopessimilar to the 6z1 are monitored forground movements, rockmass responseand subsequent seismic activity, thecurrent seismic system was reviewedand developed into an expansionproject (see Photo 1).

• The geotechnical data that wasnecessary to complete the 6z1assessment was obtained during thegeotechnical site coverage (see Photo2). This site coverage involves goodcommunication and teamwork, which isnecessary to ensure continuity acrossroster changes in order to thoroughlyassess blast ring design, draw point andaccess stability, which was indicated ascritical for 6z1.

• One of the most important aspects ofthe integrated service is the variety ofgeotechnical experience exposure tothe CBH site geotechnical engineer,especially in the late stage of mining.

• Mining of stopes like the 6z1 has animpact on regional stability. It is criticalnot to just assess the local instabilitywhen reviewing the stope for miningbut to incorporate the detailed backfillassessment highlighted below.

• Backfilling the historic mine voids ormaintaining fill height is another keychallenge of the project and consists of:

I. Local surface material propertyevaluation for dry fill placement.

II. Local surface material propertyevaluations for paste fill design andplacement through a dedicatedpaste fill reticulation system from asurface paste fill plant.

III. Studies into cement binder quantityto ensure paste fill stability and localmaterial interaction impact.

IV. Dry fill placement risk assessmentfor high fine material content whichform part of Endeavor Mine’s riskmanagement process.

Meeting the geotechnical challenges atEndeavor requires close co-operationbetween the geotechnical group and themine planning engineers. Mining engineersfrom Coffey Mining and CBH have workedclosely together to develop the mine plansand operation schedules that will underpinthe future production at Endeavor.

Risk assessments, which form a key part ofthe planning and operations approach, havebrought together expertise from CBH,Coffey Mining and other stakeholders.

Discussions covered the recovery processfrom the October 2005 stope crowncollapse. A comprehensive risk assessmentprocess (for the planned rehabilitation ofthe damaged pastefill reticulation system)from the extensive overbreak in the 6z2stope was recently completed. This riskassessment process involved senior miningand maintenance personnel from EndeavorMine and Coffey Mining, highlighting theextent of the integration model.

Technical service integration processAll the above activities involved in thegeotechnical integration process requirethorough co-ordination in order toprovide an unconstrained flow ofinformation to and from mine personnel.More important is the flow of accurateinformation between off-site and on-sitepersonnel to ensure prompt reporting forscheduling purposes. The integratedgeotechnical service success is maintainedby regular and detailed communication.

With the current skills shortage it is difficultfor companies to fully staff their operationsand maintain site information continuitywhich is vital to ensure operational risks areat an acceptable level. Traditional high levelconsulting can sometimes suffer from adisconnection with the operationalpracticalities of a producing mineenvironment. The project staffing modeldeveloped between CBH and CoffeyMining overcomes these issues by workingas an effective team with a common focus.

This model’s strength lies within thedegree of shared knowledge that is builtup over time and used when required, ona long-term basis.

For more information, please contact

[email protected].

AcknowledgementsCoffey Mining thanks CBH Resources –

Endeavor Mine, Mr. Mike Fischer (general

manager) and Mr. Stuart Pether (manager

mining) for their continued support and

permission to publish this article. Also a

special thanks to all on-site Endeavor

personnel for an extremely cooperative

working environment.

Photo 1 A geological engineer inspects the ESGPaladin seismic network

Photo 2 Good communication and teamwork arenecessary to ensure continuity across roster changes


The First International Seminar onStrategic versus Tactical Issues in Miningwas hosted by the SAIMM in South Africain September 2005. For the first timeever, the mining industry was broughttogether to reflect and exchange theirperceptions on how strategic thinking andplanning processes are handled bydifferent mining organisations and bodies,from global mining houses to smallconsultancies.

Following on from the success of theSouth African seminar, the ACG wasdelighted to host the Second InternationalSeminar on Strategic versus TacticalApproaches in Mining in Perth in March2006.This seminar provided a uniqueforum for local industry to share theirexperiences, their successes and also someof the opportunities that they may havemissed due to a lack of a long-term focus.

As Perth turned on its autumn charm,almost 150 mining professionals,consultants, researchers and suppliersgathered to explore the different theoriesand applications used by operations toachieve their long and short-term goals.Dr Bruce Hobbs, chief scientist of WAand the executive director of the Officeof Science and Innovation, Dept. ofPremier and Cabinet opened theproceedings with a keynote addressquestioning if industry can be predictive inmineral exploration.The answer was aresounding yes as long as theunderstanding is that by predictive, wemean calculable or computable.

The first day featured sessions onstrategic issues and general managementand economics, and comprehensive casestudies from BHP Billiton Nickel West andAnglo Platinum Ltd.

On day two, the highly respected industrysage Dr Oskar Steffen, SRK, presented akeynote address that reviewed strategicplanning processes and criteria forstrategic planning. Steffen concluded thatnumerical values that are meaningful canbe successfully applied to mining plans andprojects, and outcomes should be statedin terms of economic and risk results,however, the adoption of an acceptableresult is dependent upon the company’s

appetite for risk versus rewardn

Day two sessions focused onenvironmental and open pit strategies andcomprehensive case studies fromNewcrest Mining Ltd and Xstrata ZincGeorge Fisher Mine.

The presentations on the final day includedan overview of WA’s resource sector byMr Tim Shanahan from the Chamber ofMinerals and Energy of WA. According toresearch conducted by the John CurtinInstitute of Public Policy, the output of theresources is likely to grow by 50 to 75percent over the next decade. Suchgrowth will ensure that the resourcesector remains the key driver of the WAeconomy into the future.

Day three sessions included generalstrategic planning, caving strategies andunderground mining case studies, includinga detailed case study from BHP BillitonCannington.Those attending departed tothe four corners of the world, havinggained a shared knowledge and furtherinsight into the planning strategies of theirindustry and research peers.

The ACG was able to host the seminar withthe generous support and encouragementof its sponsors, namely, BHP Billiton NickelWest, Barrick Gold of Australia, SRKConsulting and Bosfa/Sika Australia.

Strategic versus Tactical 2006promoting best practices in strategic planning activities in Australian mines

ACG 2nd International Seminar on Strategicversus Tactical Approaches in MiningProceedingsThe Second International Seminar on Strategic versus Tactical Approaches in MiningProceedings contains 600+ pages featuring more than 40 papers.

Mining presents significant risks related to uncertainties, but potentially extraordinaryrewards for shareholders, industry stakeholders and society.To maximise these rewardsover the lifetime of our precious but limited mineral assets, a clever strategic approach tomining must be carefully developed and systematically implemented.

Papers from leading experts and top practitioners, including: Bob Adam (BHP Billiton), BruceHobbs (Dept. of Premier & Cabinet,WA Govt.), Michael Hood (CRCMining), Peter McCarthy(AMC Consultants),Tim Shanahan (CME) and Oskar Steffen (SRK Consulting).

To order your copy, please contact Jill at the ACG.

More than 150 mining professionals attended theseminar

3rd International Seminar on Strategicversus Tactical Approaches in Mining

The Third International Seminar onStrategic versus Tactical Approaches inMining will be held in Canada in 2007.For more information, please contactJohn Hadjigeorgiou [email protected].

At the conclusion of the third and finalseminar, the ACG will produce ahardbound publication featuring thehighest quality papers from the 2005to 2007 seminars.

Jo, this page very tight, had to delete a coupleof pics and still needs editing

The ACG is delighted to bring

the 2007 International Seminar

on Paste and Thickened Tailings

to Perth. Paste07 will explore the

latest advances in the

preparation, transportation and

deposition of paste and thickened

tailings (P&TT) that will be

reinforced by current case

studies.This seminar will also

address the important part that

P&TT plays in incremental

rehabilitation and its impact on

mine closure goals.

The seminar will provide a forum forP&TT practitioners, consultants,researchers and suppliers worldwide toexchange views on best practice andstate-of-the-art technologies.Theseseminars set the agenda for futureresearch and operational directions, andensure the ongoing viability of the miningindustry.

Key Dates Submission of abstract 7 August 2006

Submission of paper9 October 2006

ACG Rheology Workshop12 March 2007

ACG Paste07 Seminar13-15 March 2007

Waste

Paste and Thickened Tailings – A Guide (Second Edition)

The ACG wasdelighted tolaunch the Pasteand ThickenedTailings – A Guide(Second Edition) atthe NinthInternational

Seminar on Paste and ThickenedTailings held in Limerick, Ireland in April2006. An essential source ofinformation on the technology andmanagement associated with paste andthickened tailings (P&TT), this revised,full colour second edition features twonew chapters on slurry chemistry &reagents, completely rewrittenchapters on surface disposal, minebackfill and transport, the inclusion offiltering equipment for thickening and anumber of new case studies.

The ACG is grateful for the outstandingcontributions made from well knownindustry practitioners and experts fromthroughout the world. Our thanks are alsoextended to the guide’s sponsors for theirfinancial support and encouragement tobring this publication to fruition.

Level One SponsorsAran International Pty LtdDorr-Oliver EimcoLightnin AfricaMetago Environmental EngineersOutokumpu TechnologyPasteThick AssociatesSRK Consulting

Level Two SponsorsAMC ConsultantsAMEC Earth & EnvironmentalAustralian Tailings ConsultantsCoffey Mining


Paste and Thickened Tailings Updatepaste/ perst/ n.

1 a mixture of flour and water,used for sticking paper.

2 any material or preparationin a soft mass: a toothpaste.

3 Colloq. to beat and scoldsomeone.

4 Paste07 – the evolution ofpaste technology

ACG Paste05 and Paste06 Seminar ProceedingsKeep abreast of the latest P&TT technological advances andbest practice by accessing the ACG’s P&TT publicationsincluding the Paste05 and Paste06 seminar proceedings.To findout why the global mining industry turns to the ACG as themain source of P&TT knowledge, contact the ACG for adetailed list of P&TT publications and seminar/ workshopproceedings.


Although Europe may no longer be thecentre of mining activity, the seminarcontent was clearly enough motivation toattract a large gathering of delegates fromaround the world.The number ofdelegates had to be capped at 175 andaccording to the conference organisersthey could have taken at least another 50bookings.This level of interest is a clearindication of the ongoing interest in thetechnology of high density tailingspreparation, transport and management. Ifanything, interest is likely to increase inthe future, with regulatory requirementsfor the management of mine tailingsbecoming ever more severe.

The seminar programme includedkeynote addresses by: Peter Scales,University of Melbourne, onUnderstanding the thickening process;Ted Lord, Syncrude Canada and JohnOxenford, John Oxenford & Associates,on Canadian Experience in the applicationof paste and thickened tailings for surfacedisposal; and Dave Landriault, GolderPaste Technology Ltd, on, They said it willnever work – 25 years of paste backfill1981-2006. As indicated by the titles,these three presentations covered mostof the primary areas of interest ofdelegates attending the seminar ; fromadvances in understanding the thickening

process (where Peter clearly pointed outsome of the deficiencies in ourunderstanding as well as some of thesuccesses), through surface disposal insometimes hostile circumstances, tomaking underground backfilling usingpaste technology work in circumstanceswhere it had been rejected by all but themost ardent believers in the technology.The technical programme that followed,included over 30 presentations on topicsrelated to the above keynote lectures, aswell as issues of safe and economicaltransport of high density slurries.

An interesting aspect of the presentationswas the number of operations that arenow either using high density thickenedtailings for surface deposition, or are in anadvanced stage of implementing thetechnology. Only a few years ago peoplewere asking, ‘show me where it isworking?’, whereas now the questions aremore likely to be, ‘how well is it working?’or, ‘how much water are you actuallysaving?’. Many of the presentations at theseminar provided answers to some ofthese questions and it was pleasing to seethat some of the touted benefits of P&TTare indeed being realised, such as verysignificant water savings in some instances.Another enduring criticism of P&TT thatwas shown to be incorrect is the

Paste 06 – goes the distanceThe grey skies of south-west Ireland cleared during the week of 3rd to

7th April, providing an ideal welcome to delegates attending the 9th

International Seminar on Paste and Thickened Tailings (P&TT).

The seminar was held in Limerick, which provided an extremely

appropriate setting, with two operations utilising high density tailings

within easy reach of the city.

Paste 2006 presented an insight into tailings activities in Ireland

Paste07 will explore the latest advances in thepreparation, transportation and deposition of P&TT.Photo courtesy of De Beers


supposition that the technology can only

be applied to new operations (green field

sites). At a number of operations,

particularly in Canada, existing

conventional tailings management

operations have been converted, very

successfully, to high density thickened

tailings operations.

Advances in thickener technology were

discussed at some length and interesting

developments in the ability to pump

higher and higher yield stress materials

using centrifugal pumps were presented.

Clearly the technology continues to

improve at a rapid rate. Improvements in

our understanding of post-deposition

behaviour of thickened tailings on surface

are being made possible by the extensive

monitoring and testing that is occurring at

some sites, and some very useful

information was presented during the

seminar. It also appears that designers are

coming around to a better understanding

of the risks posed by the potential

liquefaction and instabilities of the

deposits that result from the

implementation of P&TT on surface.

The seminar was preceded by a one-day

workshop on the intricacies and delights

of rheology, with an opportunity to play in

the mud (in the laboratory of course)

being provided during an afternoon

session hosted by the University of

Limerick.These workshops are becoming

a regular feature of the seminars and

provide an ideal opportunity for those

who are relatively new to the field of

P&TT to quickly get up to speed before

the start of the seminar proper.

The week was rounded off by two site

visits.The sites visited were the Aughinish

Island alumina refinery site, where bauxite

from Brazil and west Africa is refined to

produce alumina and the residual red

mud is managed using an innovative

thickening and disposal operation, and the

Lisheen mine, where paste tailings are

placed underground at a very high rate,

with the final goal being in excess of 80%

tailings going back underground. Both

operations exhibited highly advanced

implementations of the latest technology

and, in the case of the surface deposition

of red mud, showed that the technology

can indeed be made to work in (very!)

wet climates and still be viable.

The seminar organisers, in particular Phil

Newman from Golder Associates, Liam

McNamara of Dorr-Oliver Eimco and

Simon Lawson from the Industrial Centre

of Particle Science and Engineering at

Leeds University, are to be congratulated

on facilitating a gathering at which an

enormous amount of valuable networking

and sharing of experiences was made

possible, during both the formal sessions

and the equally valuable breakout sessions

and social functions.

Next year P&TT goes back to its roots,

with the 10th International Seminar to be

held in Perth from the 13th to 15th

March 2007.The historic city of Fremantle

will provide the venue for what is likely to

be a vibrant and valuable seminar, with

many more new and innovative

technologies and case studies being

showcased. Once again, the venue size

will be limited so early registration for this

event is advisable. For further information,

visit www.paste07.com.

The Ground Control Group of WA’s (GCGWA) first meeting for the

year was held in Kalgoorlie in March.The group meets three times a

year as an independent and impartial body enabling underground and

open pit geotechnical engineers to meet, discuss and exchange ideas,

techniques and experiences in a technical yet informal setting. It also

provides a forum for attendees to discuss ground conditions specific

to their own sites and to seek the opinions and recommendations of

their peers.

At last month’s meeting the group decided to retain the independent and impartial

status of the group, in that membership is limited to mining practitioners only.

However, membership is now open to industry professionals that either work for,

or are a representative, of a mining company.

Additionally, mine training departments will be encouraged to view GCGWA

membership as a means of advancing staff development through networking and

interacting with peers from other sites.

For more details about the March meeting or to register your interest to attend the

next meeting to be held in Kalgoorlie in June/ July 2006, please contact the ACG.

UpdateGroup Control

Group ofWesternAustralia

10th International Seminar on Paste 13-15 March 2007 The Esplanade Hotel, Fremantle,and Thickened Tailings Perth, WA

2007 International Symposium on Rock Slope 12-14 September 2007 Sheraton Perth Hotel,WAStability in Open Pit Mining and Civil Engineering

Economic Risk & Project Evaluation, and 21-23 February 2007 Novotel Brisbane, QldGeomechanics Risk Management

Caving Geomechanics 1-2 March 2007 Ibis Perth Hotel,WA

10th International Seminar on Paste and 13-15 March 2007 The Esplanade Hotel, Fremantle,Thickened Tailings Perth WA

Stope Planning and Design and Case Histories 2-4 May 2007 Ibis Perth Hotel,WA

Water Management Seminar 12-13 June 2007 Ibis Perth Hotel,WA

Mine Closure for Decision Makers 14-15 June 2007 Ibis Perth Hotel,WA

High Density Transport 1-2 August 2007 Ibis Perth Hotel,WA

Mine Fill 3 August 2007 Ibis Perth Hotel,WA

International Symposium on Rock Slope Stability 12-14 September 2007 Sheraton Perth Hotel,WAin Open Pit Mining and Civil Engineering

Sirovision User’s Conference – Open Pit and 11 September 2007 Sheraton Perth Hotel,WAUnderground Applications

Advanced Ground Support 6-9 November 2007 Ibis Perth Hotel,WA

An Introduction to Soil Mechanics 5 December 2007 Ibis Perth Hotel,WA

Tailings Management and Decommissioning 6-7 December 2007 Ibis Perth Hotel,WA


ACG 2006 – 2007 Event Schedule*

Title Date Where

* The ACG event schedule is subject to change.

Australian Centre for Geomechanics PO Box 3296 – Broadway, Nedlands,Western Australia, AUSTRALIA 6009Ph + 61 8 6488 3300 Fax +61 8 6488 1130 [email protected] www.acg.uwa.edu.au

Abstracts due Monday 7 August 2007

Paste07 will explore the latest advances in the preparation, transportation and depositionof P&TT that will be reinforced by current case studies.The part that P&TT plays inincremental rehabilitation and its impact on mine closure goals will also be addressed.Contact Andy or Jo at the ACG for further details.

www.paste07.com

Paste 2007 13 – 15 March 2007, Perth,WA

logo to be addedonce finalised

Development and Production Blasting 2-3 August 2006 Ibis Perth Hotel,WAin Underground Mines

Preparing and Implementing a Tailings Storage 11 September 2006 Sheraton Perth Hotel,WAFacility Operations Manual

First International Seminar on Mine Closure 13-15 September 2006 Sheraton Perth Hotel,WA

Blasting for Stable Slopes 5-6 October 2006 Ibis Perth Hotel,WA

Ground Support in Open Pit and 31 Oct-3 Nov 2006 Ibis Perth Hotel,WAUnderground Mines

Geosynthetics in Mining Seminar 6-8 December 2006 Ibis Perth Hotel,WA

Filling the Gap – a Geomechanics Perspective

Documents

Transcript of Filling the Gap – a Geomechanics Perspective