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

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Scaling and bolting or shotcrete

Scaling and Bolting or Shotcrete


56 57 3000 definitions

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 definitions1

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

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

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

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

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

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

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.


Scaling and bolting or shotcrete

Scaling

Hand verses Mechanical Scaling

Scaling Bar

Mechanical Scaler


Scaling and bolting or shotcrete

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.

Effectiveness dependent upon the skill and experience of personnel

Economical


Scaling and bolting or shotcrete

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


Scaling and bolting or shotcrete

Data from underground mines in Sweden


Scaling and bolting or shotcrete

ROOF BOLTING

Scaling

Shotcrete


Scaling and bolting or shotcrete

Rock Bolt Installation

More versatile

Costly

Limited

Inexpensive


56 57 3203 rock fixtures

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--


56 57 3203 rock fixtures1

56 & 57.3203 Rock Fixtures.

  • (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?


56 57 3203 rock fixtures2

56 & 57.3203 Rock Fixtures.

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


56 57 3203 rock fixtures3

56 & 57.3203 Rock Fixtures.

  • (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


56 57 3203 rock fixtures4

56 & 57.3203 Rock Fixtures.

  • (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.


56 57 3203 rock fixtures5

56 & 57.3203 Rock Fixtures.

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


56 57 3203 rock fixtures6

56 & 57.3203 Rock Fixtures.

  • (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 bolting

Roof Bolting

Roof Bolting

  • Support Principles

  • Support Parameters

  • Shotcrete


Bolting principles

Bolting Principles

What is the Bolt System Designed to do?

  • Beam building

  • Suspension

  • Keying

  • Surface control - natural arch


Beam building

Laminated

Strata

Weak

Strata

Support Principles

Beam Building

Individual laminations bound together to form a single beam


Suspension

Anchorage Zone

Support Principles

Suspension

Competent

Strata

Weak

Strata

Suspended layer


Keying

Support Principles

Keying

Fractured

Rock

Weak

Strata


Scaling and bolting or shotcrete

Surface Control

Support Principles

Highly jointed, altered or

weathered rock


Bolting principles1

Bolting Principles

  • Beam building

  • Suspension

  • Keying

  • Surface control - naturalarch


Critical parameters

Critical Parameters

  • Bolt Type

  • Strength

    • Grade

    • Diameter

  • Length

  • Density (spacing)

  • Plate


Types of bolts

Types of Bolts

  • Friction Anchored

  • Mechanical

  • Fully Grouted

  • Tensioned Rebar

  • Combination/Point Anchored

  • Mechanically Anchored/Resin Assisted


Scaling and bolting or shotcrete

Support Characteristics

* Anchorage

* Clamping

* Vertical Stiffness

* Horizontal Stiffness


Scaling and bolting or shotcrete

Friction Anchored Support

Splitsets or Swellex Bolts

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


Scaling and bolting or shotcrete

FRICTION ANCHORED BOLTS

SPLIT TUBE

EXPANDING TUBE


Mechanisms of friction anchor bolts

MECHANISMS OF FRICTION ANCHOR BOLTS

LOW ANCHORAGE

DEVELOPED ALONG

BOLT LENGTH

LITTLE OR NO SHEAR

RESISTANCE ALONG

SLIPS AND JOINTS

UNLESS INTERSECTED

BY BOLT

NO CLAMP

LOADS

LOW PLATE LOADS


Scaling and bolting or shotcrete

Split Sets

Inexpensive

Easy to Install

No resin cartridges

Can be installed in soft or shifting ground


Splitset

SPLITSET


Radial force

RADIAL FORCE


Swellex

SWELLEX


Dywidag bolt

DYWIDAG BOLT


Scaling and bolting or shotcrete

Friction Anchor Bolts


Critical parameters1

Critical Parameters

  • Bolt Type

  • Strength

    • Grade

    • Diameter

  • Length

  • Density (spacing)

  • Plate


Expansion shell anchor bolt

EXPANSION SHELL ANCHOR BOLT


Parts of a 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

PARTS OF A BOLT cont.

  • WASHER

    • ACTS AS LUBRICATION BETWEEN PLATE AND BOLT HEAD


What does grade of a bolt mean

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

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

Grade 55

5/8 INCH

DIAMETER

ROOF BOLT HEAD MARKING

5


Roof bolt markings

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


Scaling and bolting or shotcrete

MECHANICAL BOLTS

Plugs

Bail

Shell Leaves

Support Nut

Bolts

BAIL STANDARD


Standard 4 leaf type expansion shell

STANDARD 4 LEAF TYPE EXPANSION SHELL


Three prong expansion shell

THREE PRONG EXPANSION SHELL


Two leaf bail type expansion shell

TWO LEAF BAIL TYPE EXPANSION SHELL


Scaling and bolting or shotcrete

JAM NUT

TO STRONG


Scaling and bolting or shotcrete

  • JAM NUT

  • TOO STRONG

  • ( DOES NOT

  • BREAK AWAY

  • AND DEFORMS

  • THE SHELL )


Deformed shell

DEFORMED SHELL


Scaling and bolting or shotcrete

JAM

NUT

TOO

WEAK


Scaling and bolting or shotcrete

  • JAM NUT

  • TOO WEAK

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


56 57 3203 rock fixtures7

56 & 57.3203 Rock Fixtures.

  • (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


56 57 3203 rock fixtures8

56 & 57.3203 Rock Fixtures.

  • (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

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

KFACTOR 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 strength

BOLT STRENGTH


Mechanisms of mechanical bolts

MECHANISMS OF MECHANICAL BOLTS

MODERATE TO HIGH ANCHORAGE DEPENDING ON THE STRATA

MODERATE

CLAMP

LOADS

CLAMP LOADS DEVELOP

SOME SHEAR RESISTANCE

ALONG BEDDING PLANES,

SLIPS AND JOINTS

MODERATE PLATE LOADS


56 57 3203 rock fixtures9

56 & 57.3203 Rock Fixtures.

  • (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.


Scaling and bolting or shotcrete

FULLY GROUTED BOLTS


56 57 3203 rock fixtures10

56 & 57.3203 Rock Fixtures.

  • (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.


56 57 3203 rock fixtures11

56 & 57.3203 Rock Fixtures.

  • (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

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

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 cont1

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 cont2

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 cont3

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 bolts

NO CLAMP

LOADS

HIGH ANCHORAGE

DEVELOPED ALONG

BOLT LENGTH

MECHANISMS OF FULLY GROUTED BOLTS

HIGH SHEAR RESITANCE

ALONG RESIN/ROCK

INTERFACE

LITTLE OR NO SHEAR

RESISTANCE ALONG

SLIPS AND JOINTS

UNLESS INTERSECTED

BY BOLT

LOW PLATE LOADS


Resin anchor torque tension bolt

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 bolt1

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


Scaling and bolting or shotcrete

TENSIONED REBAR

Threaded

Deformed

Bar

Aluminum Plug

Cast Dome

Shear Pin

Tension Nut

TENSION NUTS


Mechanisms of tensioned rebar bolts

MECHANISMS OF TENSIONED REBAR BOLTS

EXTREMELY HIGH

ANCHORAGE REGARD-

LESS OF STRATA

HIGH SHEAR RESISTANCE

ALONG RESIN/ROCK

INTERFACE

VERY HIGH

CLAMP LOADS

CLAMP LOAD DEVELOPS

VERY HIGH SHEAR

RESISTANCE ALONG

SLIPS AND JOINTS

VERY HIGH PLATE LOADS


Scaling and bolting or shotcrete

MECHANICAL BOLTS

(RESIN ASSISTED)

Compression Tube

Deformed Bar

Mechanical Bolt


Resin point anchor with rebar supplement

RESIN POINT ANCHOR WITH REBAR SUPPLEMENT


Resin point anchor with steel pipe supplement

RESIN POINT ANCHOR WITH STEEL PIPE SUPPLEMENT


Resin point anchor with shear pin compression ring

RESIN POINT ANCHOR WITH SHEAR PIN & COMPRESSION RING


Mechanisms of point resin anchored bolts

MECHANISMS OF POINT RESIN ANCHORED BOLTS

HIGH ANCHORAGE EVEN IN SOFT ROCK

CLAMP LOADS DEVELOP

MODERATE SHEAR

RESISTANCE ALONG BEDDING

PLANES,SLIPS AND JOINTS

HIGH

CLAMP

LOADS

HIGH PLATE LOADS


Scaling and bolting or shotcrete

COMBINATION BOLT

Threaded

Deformed

Bar

Grout

Column

Tensioning

Coupler

Shear

Pin

Bearing Plate


What is a shear pin

WHAT IS A SHEAR PIN ?


Mechanisms of combination bolts

EXTREMELY HIGH

ANCHORAGE REGARDLESS

OF STRATA

MECHANISMS OF COMBINATION BOLTS

GROUTED LENGTH

REINFORCES THE STRATA

LIKE A FULLY GROUTED BOLT

VERY HIGH

CLAMP LOADS

CLAMP LOADS DEVELOPS

HIGH SHEAR RESISTANCE

ALONG BEDDING PLANES,

SLIPS AND JOINTS

VERY HIGH PLATE LOADS


Support characteristics

Mechanical

Moderate

Moderate

Low

Low

Fully

Grouted

Medium/

High

Very

High

Low

High

Point

Anchor

Low/

Medium

Medium

High

High

High

Medium/

High

Very

High

Very

High

Combination

Very

High

Tensioned

Rebar

Very

High

Very

High

Very

High

Support Characteristics

Vertical

Stiffness

Horizontal

Stiffness

Bolt Type

Anchorage

Clamping

Frictional

Anchors

Low

Low

Low

Low


Scaling and bolting or shotcrete

Full Contact Supports

Anchorage Length

* Resin Anchored

* Friction Anchored

(Split Sets, Swellex, Friction Loc)


Scaling and bolting or shotcrete

Friction Anchor

Resin Anchor

1 Ton Per Foot

10 Tons+ Per Foot


Scaling and bolting or shotcrete

Anchorage Variable

Along Bolt Length

Anchorage Constant

Along The Bolt Length

FULL CONTACT

SUPPORT

POINT ANCHORED

SUPPORT


Scaling and bolting or shotcrete

Anchorage

1 Ton/Ft.

(10 Tons)

Anchorage

10 Tons

10’

FRICTION ANCHORED

SUPPORT

(SPLIT SET)

POINT ANCHORED

SUPPORT

(MECHANICAL BOLT)


Scaling and bolting or shotcrete

Anchorage

1 Ton/Ft

(8 Tons)

Anchorage

10 Tons

8’

10’

FRICTION ANCHORED

SUPPORT

POINT ANCHORED

SUPPORT


Scaling and bolting or shotcrete

1’

Anchorage

1 Ton/Ft

(1 Ton)

Anchorage

10 Tons

10’

FRICTION ANCHORED

SUPPORT

POINT ANCHORED

SUPPORT


Critical parameters2

Critical Parameters

  • Bolt Type

  • Strength

    • Grade

    • Diameter

  • Length

  • Density (spacing)

  • Other hardware (plates, washers, straps)


Bolt strength1

Bolt Strength

Rock Bolts

5/8” Grade 55

19,200lbs.

1-1/8” Grade 100

95,400lbs.

Friction Anchored Bolts

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

Cable Bolts

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


Break time

Break Time


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