Scaling and Bolting or Shotcrete 56 & 57.3000 Definitions. The following definitions apply in this...

Scaling and Bolting or Shotcrete

56 & 57.3000 Definitions.

• The following definitions apply in this subpart.

• Rock burst. A sudden and violent failure of overstressed rock resulting in the instantaneous release of large amounts of accumulated energy. Rock burst does not include a burst resulting from pressurized mine gases.

56 & 57.3000 Definitions.

• Rock fixture. Any tensioned or nontensioned device or material inserted into the ground to strengthen or support the ground.

• Travelway. A passage, walk, or haulageway regularly used or designated for persons to go from one place to another.

56 & 57.3200 Correction of Hazardous Conditions

• Ground conditions that create a hazard to persons shall be taken down or supported before other work or travel is permitted in the affected area. Until corrective work is completed, the area shall be posted with a warning against entry and, when left unattended, a barrier shall be installed to impede unauthorized entry.

56\57.3200 PPM

• This standard prohibits work or travel, other than corrective work, in areas where hazardous ground conditions exist. Posting of a warning against entry is required until corrective work is completed if workers could enter the area inadvertently.

56\57.3200 PPM Cont.

• In addition, barriers are required if the area is left unattended prior to the completion of the corrective work. The mode of travel in the area must be evaluated to determine what type of barrier is appropriate to "impede" unauthorized entry.

56\57.3200 PPT Cont.• Examples of barriers would be piles of muck,

piles of large boulders or a timber barricade. These barriers would have openings to allow access for persons who are correcting the hazardous conditions. These posting and barrier requirements do not apply to underground face areas under development where the corrective work is performed on a continuing basis as a part of the mining cycle, and the only workers exposed are those engaged in the corrective activity.

56 & 57.3201 Location for Performing Scaling.

• Scaling shall be performed from a location which will not expose persons to injury from falling material, or other protection from falling material shall be provided.

56 & 57.3202 Scaling Tools.

• Where manual scaling is performed, a scaling bar shall be provided. This bar shall be of a length and design that will allow the removal of loose material without exposing the person performing the work to injury.

Hand verses Mechanical Scaling

Scaling Bar

Mechanical Scaler

Scaling

Hand Scaling

Allows for a detailed assessment of rockmass

integrity by close observation and “feeling

the rock”

Allows the back to be sounded by hand.

Economical

Effectiveness dependent upon the skill and

experience of personnel

Mechanical Scaling

Allows operators to maintain a safer distance from area being scaled.

Can reach higher into back or fall cavities.

Applies greater force to loose blocks

Data from underground mines in Sweden

ScalingScaling

ShotcreteShotcrete

Rock Bolt Installation

Limited

More versatile

Inexpensive

Costly

56 & 57.3203 Rock Fixtures.

• (a) When rock bolts and accessories addressed in ASTM F432-95, "Standard Specification for Roof and Rock Bolts and Accessories", are used for ground support, the mine operator shall--


• (1) Obtain a manufacturer's certification that the material was manufactured and tested in accordance with the specifications of ASTM 432-95; and,

• Where does MSHA test these bolts?


• (2) Make this certification available to an authorized representative of the Secretary.


• (b) Fixtures and accessories not addressed in ASTM F432-95 may be used for ground support provided they-

• (1) Have been successful in supporting the ground in an area with similar strata, opening dimensions and ground stresses in any mine; or


• (2) Have been tested and shown to be effective in supporting ground in an area of the affected mine which has similar strata, opening dimensions, and ground stresses as the area where the fixtures are expected to be used. During the test process, access to the test area shall be limited to persons necessary to conduct the test.


• (c) Bearing plates shall be used with fixtures when necessary for effective ground support.


• (d) The diameter of finishing bits shall be within a tolerance of plus or minus 0.030 inch of the manufacturer's recommended hole diameter for the anchor used. When separate finishing bits are used, they shall be distinguishable from other bits.

Roof BoltingRoof Bolting

• Support PrinciplesSupport Principles

• Support ParametersSupport Parameters

• ShotcreteShotcrete

Bolting PrinciplesBolting Principles

• Beam buildingBeam building

• SuspensionSuspension

• KeyingKeying

• Surface control - natural archSurface control - natural arch

What is the Bolt System Designed to do?What is the Bolt System Designed to do?

Beam BuildingBeam Building

WeakStrata

LaminatedLaminatedStrataStrata

Individual laminations bound together to form a

single beam

Support Principles

SuspensionSuspensionCompetent

Strata

WeakStrata

Anchorage Zone

Support Principles

Suspended layer

KeyingKeying

WeakStrata

FracturedFractured RockRock

Support Principles

Surface ControlSurface Control

Highly jointed, altered orHighly jointed, altered orweathered rockweathered rock

Support Principles

Bolting PrinciplesBolting Principles

• Beam buildingBeam building

• SuspensionSuspension

• KeyingKeying

• Surface control - naturalSurface control - natural archarch

Critical ParametersCritical Parameters• Bolt TypeBolt Type• StrengthStrength

–GradeGrade–DiameterDiameter

• LengthLength• Density (spacing)Density (spacing)• PlatePlate

Types of BoltsTypes of Bolts

• Friction Anchored Friction Anchored

• MechanicalMechanical

• Fully GroutedFully Grouted

• Tensioned RebarTensioned Rebar

• Combination/Point AnchoredCombination/Point Anchored

• Mechanically Anchored/Resin AssistedMechanically Anchored/Resin Assisted

Support CharacteristicsSupport Characteristics

* AnchorageAnchorage

* Clamping* Clamping

* Vertical Stiffness* Vertical Stiffness

* Horizontal Stiffness* Horizontal Stiffness

Split sets provide minimal support (~1 ton Split sets provide minimal support (~1 ton per foot of anchorage) when utilized in a per foot of anchorage) when utilized in a

suspension application.suspension application.

Friction Anchored SupportFriction Anchored Support

Splitsets or Swellex BoltsSplitsets or Swellex Bolts

FRICTION ANCHORED BOLTS

SPLIT TUBE

EXPANDING TUBE

MECHANISMS OF FRICTION ANCHOR BOLTSMECHANISMS OF FRICTION ANCHOR BOLTS

LOW PLATE LOADS

LOW ANCHORAGEDEVELOPED ALONG

BOLT LENGTH

NO CLAMP LOADS

LITTLE OR NO SHEARRESISTANCE ALONGSLIPS AND JOINTS

UNLESS INTERSECTEDBY BOLT

Split Sets

InexpensiveInexpensive

Easy to InstallEasy to Install

No resin cartridgesNo resin cartridges

Can be installed in soft or shifting groundCan be installed in soft or shifting ground

SPLITSET

RADIAL FORCE

SWELLEX

DYWIDAG BOLT

Friction Anchor Bolts

Critical ParametersCritical Parameters• Bolt TypeBolt Type• Strength

– Grade– Diameter

• Length

• Density (spacing)

• Plate

EXPANSION SHELL ANCHOR BOLT

PARTS OF A BOLT

• SHELL– STANDARD ( HARD ROOF )– BAIL ( SOFT ROOF )

• PLUG– SPREADS SHELL

• SUPPORT NUT (PAL NUT or JAM NUT)– HOLDS SHELL IN PLACE - THEN

BREAKS AWAY

PARTS OF A BOLT cont.

• WASHER– ACTS AS LUBRICATION BETWEEN

PLATE AND BOLT HEAD

WHAT DOES GRADE OF A BOLT MEAN ?

• GRADE 75 MEANS THE BOLT HAS A TENSILE STRENGTH 75,000 PSI– TENSION BOLTS

• GRADE 60 MEANS THE BOLT HAS A TENSILE STRENGTH 60,000 PSI– NONTENSION BOLTS

WHAT DOES THE TERM #5 REBAR MEAN ?

• THE DIAMETER OF BOLT ARE STAMPED IN 1/8 INCH INCREMENTS

• SO A #5 HAS A DIAMETER OF 5/8 INCH

• A CIRCLE AROUND THE NUMBER MEANS IT IS A DEFORMED BAR

• 5/8 INCH REBAR = 5

ROOF BOLT HEAD MARKING

5 Grade 55 5/8 INCHDIAMETER

ROOF BOLT MARKINGS

GRADE DIAMETER DESIGNATION

40 3/4 INCH UP NONE

55 5/8 INCH UP

60 5/8 INCH UP

75 5/8 INCH UP X

100 5/8 INCH UP

Plugs

Shell LeavesSupport Nut

Bolts

Bail

BAIL STANDARD

STANDARD 4 LEAF TYPE EXPANSION SHELL

THREE PRONG EXPANSION SHELL

TWO LEAF BAIL TYPE EXPANSION SHELL

JAM NUTTO STRONG

• JAM NUT

• TOO STRONG• ( DOES NOT

• BREAK AWAY

• AND DEFORMS

• THE SHELL )

DEFORMED SHELL

JAMNUTTOO

WEAK

• JAM NUT

• TOO WEAK

• ( BREAKS AWAY TOO SOON AND DOES NOT EXPAND SHELL )


• (f) When rock bolts tensioned by torquing are used as a means of ground support,

• (1) Selected tension level shall be-

• (i) At least 50 percent of either the yield point of the bolt or anchorage capacity of the rock, whichever is less; and


• (ii) No greater than the yield point of the bolt or anchorage capacity of the rock.

• WHAT IS ANCHORAGE CAPACITY OF THE ROCK & HOW DO WE MEASURE IT?

WHAT IS THE RELATIONSHIP BETWEEN THE WASHER AND THE TENSION IN THE BOLT ?

• THE “K” FACTOR IS THE RELATIONSHIP BETWEEN THE WASHER & TENSION IN BOLT

• NO WASHER K = 40

• HARDENED WASHER K = 50

• ANTIFRICTION WASHER K = 75 > 125» HARD PLASTIC

K FACTOR cont.

• TENSION IN BOLT = K x TORQUE

• FOR A BOLT USING A HARDEN WASHER AND HAS A TORQUE OF 150 FT- LBS

• TENSION IN BOLT = 50 x 150

• TENSION IN BOLT = 7500 LBS

BOLT STRENGTHBOLT DIA & GRADE

MINIMUMYIELD

ULTIMATESTRENGTH

5/8 GRADE 55 12,400 lbs 19,200 lbs

5/8 GRADE 75 17,000 22,600

¾ GRADE 75 25,100 33,400

#6 REBAR GRADE 40 17,600 30,800

#6 REBAR GRADE 60 26,400 39,600

#7 REBAR GRADE 40 24,000 42,000

#7 REBAR GRADE 60 36,000 54,000

MECHANISMS OF MECHANICAL BOLTSMECHANISMS OF MECHANICAL BOLTS

MODERATE CLAMPLOADS

MODERATE PLATE LOADS

MODERATE TO HIGH ANCHORAGE

DEPENDING ON THE STRATA

CLAMP LOADS DEVELOPSOME SHEAR RESISTANCEALONG BEDDING PLANES,SLIPS AND JOINTS


• (2) The torque of the first bolt, every tenth bolt, and the last bolt installed in each work area during the shift shall be accurately determined immediately after installation. If the torque of any fixture tested does not fall within the installation torque range, corrective action shall be taken.


• (g) When grouted fixtures can be tested by applying torque, the first fixture installed in each work place shall be tested to withstand 150 foot-pounds of torque. Should it rotate in the hole, a second fixture shall be tested in the same manner. If the second fixture also turns, corrective action shall be taken.


• (h) When other tensioned and nontensioned fixtures are used, test methods shall be established and used to verify their effectiveness.

• (i) The mine operator shall certify that tests were conducted and make the certification available to an authorized representative of the Secretary.

56\57.3203 Rock Fixtures PPM

• This standard contains the requirements for installation and testing of all rock fixtures and accessories used for ground support. In all cases where rock fixtures are selected as the method used to support ground, they must meet the requirements of 56/57.3203.

56\57.3203 PPM Cont.

• All bolts tensioned by torquing must be within the torque range set out in paragraph (f)(1). Mine operators are required to test the first, tenth and last bolt installed in each work area during the shift as a check on whether or not the torquing requirements are being achieved. When the testing process reveals that a fixture is not properly torqued, steps must be taken to determine the extent of defective installation and to correct all improperly installed fixtures.

56\57.3203 PPM Cont.

• The ground conditions in many active face areas require the installation of only a few bolts during each blasting cycle. Testing of the first and last bolts in each work area will help ensure the integrity of the ground in these instances. Where large numbers of bolts are installed on a continuing basis, testing of the first, tenth and last bolt in each work area would normally provide the frequency of testing necessary to identify a bolting problem and enable the operator to take corrective action.

56\57.3203 PPM Cont.

• The mine operator must certify that all tests required by this standard have been conducted. In the case of testing of the ASTM bolts and accessories by the manufacturer of the devices, the mine operator's certification responsibility is satisfied by obtaining a copy of the manufacturer's certification and making it available to the inspector

56\57.3203 PPM Cont.

• The correction of improperly installed fixtures will also help to ensure compliance with standard 56.3130 which requires that wall, bank and slope stability be maintained at surface mines where miners are exposed, and standard 57.3360, which requires that ground support systems at underground mines be designed, installed and maintained to control the ground where miners are exposed.

MECHANISMS OF FULLY GROUTED BOLTSMECHANISMS OF FULLY GROUTED BOLTS

LOW PLATE LOADS

HIGH ANCHORAGEDEVELOPED ALONG

BOLT LENGTH

NO CLAMP LOADS

LITTLE OR NO SHEARRESISTANCE ALONGSLIPS AND JOINTS

UNLESS INTERSECTEDBY BOLT

HIGH SHEAR RESITANCEALONG RESIN/ROCK

INTERFACE

RESIN ANCHOR TORQUE TENSION BOLT

• IN THE FIRST TYPE OF INSTALLATION, TWO FOOT OF FAST SETTING RESIN IS USED, AND THE REST OF THE HOLE IS LEFT OPEN

RESIN ANCHOR TORQUE TENSION BOLT

• SECOND TYPE, ONE TO TWO FOOT OF FAST SETTING RESIN IS PUT IN THE BACK OF THE HOLE, WHILE SLOW SETTING RESIN IS PUT IN THE BOTTOM OF THE HOLE

Aluminum Plug

Cast Dome

Shear Pin Tension Nut

ThreadedDeformed

Bar

TENSION NUTS

MECHANISMS OF TENSIONED REBAR BOLTSMECHANISMS OF TENSIONED REBAR BOLTS

VERY HIGH PLATE LOADS

EXTREMELY HIGHANCHORAGE REGARD-

LESS OF STRATA

VERY HIGHCLAMP LOADS

CLAMP LOAD DEVELOPSVERY HIGH SHEAR

RESISTANCE ALONGSLIPS AND JOINTS

HIGH SHEAR RESISTANCEALONG RESIN/ROCK

INTERFACE

Compression Tube

Deformed Bar

Mechanical Bolt

RESIN POINT ANCHOR WITH REBAR SUPPLEMENT

RESIN POINT ANCHOR WITH STEEL PIPE SUPPLEMENT

RESIN POINT ANCHOR WITH

SHEAR PIN & COMPRESSION RING

HIGH CLAMPLOADS

MECHANISMS OF POINT RESIN ANCHORED BOLTSMECHANISMS OF POINT RESIN ANCHORED BOLTS

HIGH PLATE LOADS

HIGH ANCHORAGE EVEN IN SOFT ROCK

CLAMP LOADS DEVELOP

MODERATE SHEAR RESISTANCE ALONG

BEDDING PLANES,SLIPS AND

JOINTS

GroutColumn

ThreadedDeformed

Bar

TensioningCoupler

ShearPin

Bearing Plate

WHAT IS A SHEAR PIN ?

MECHANISMS OF COMBINATION BOLTS

VERY HIGHCLAMP LOADS

VERY HIGH PLATE LOADS

EXTREMELY HIGHANCHORAGE REGARDLESS

OF STRATA

GROUTED LENGTH REINFORCES THE STRATA

LIKE A FULLY GROUTED BOLT

CLAMP LOADS DEVELOPSHIGH SHEAR RESISTANCE ALONG BEDDING PLANES,

SLIPS AND JOINTS

Support CharacteristicsSupport Characteristics

FullyGrouted

Mechanical

Combination

PointAnchor

TensionedRebar

Very High

Moderate

VeryHigh

High

VeryHigh

Low

Moderate

VeryHigh

High

VeryHigh

High

Low

Medium/High

Low/Medium

VeryHigh

Medium/High

Low

High

Medium

VeryHigh

Anchorage ClampingVertical

StiffnessHorizontalStiffness

FrictionalAnchors

Low Low Low Low

Bolt Type

Full Contact SupportsFull Contact Supports

Anchorage LengthAnchorage Length

* Resin AnchoredResin Anchored

* Friction Anchored* Friction Anchored ((Split Sets, Swellex, Friction Loc)Split Sets, Swellex, Friction Loc)

Friction AnchorFriction Anchor Resin AnchorResin Anchor10 Tons+ Per Foot10 Tons+ Per Foot1 Ton Per Foot1 Ton Per Foot

Anchorage ConstantAlong The Bolt Length

Anchorage VariableAlong Bolt Length

FULL CONTACT SUPPORT

POINT ANCHORED SUPPORT

FRICTION ANCHORED SUPPORT (SPLIT SET)


(MECHANICAL BOLT)

10’

Anchorage 1 Ton/Ft. (10 Tons)

Anchorage 10 Tons

FRICTION ANCHORED SUPPORT


10’

Anchorage 1 Ton/Ft (8 Tons)

Anchorage 10 Tons8’

FRICTION ANCHORED SUPPORT


10’

Anchorage 1 Ton/Ft (1 Ton)

Anchorage 10 Tons

1’

Critical ParametersCritical Parameters• Bolt Type

• Strength– Grade– Diameter

• Length

• Density (spacing)

• Other hardware (plates, washers, straps)

Bolt StrengthBolt Strength

Friction Anchored BoltsFriction Anchored Bolts

Rock BoltsRock Bolts

Cable BoltsCable Bolts

5/8” Grade 55 19,200lbs.

1-1/8” Grade 100 95,400lbs.

Ring Strength - 20,000 - 27,000lbs.

.6” strand - 60,000lbs. .7” strand - 70,000lbs.

Break Time

Scaling and Bolting or Shotcrete 56 & 57.3000 Definitions. The following definitions apply in this...

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