Scaling and Bolting or Shotcrete

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Scaling and Bolting or Shotcrete
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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Scaling
Hand verses Mechanical Scaling
Scaling Bar
Mechanical Scaler
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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
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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
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Data from underground mines in Sweden
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ROOF BOLTING
Scaling Shotcrete
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Rock Bolt Installation
More versatile
Costly
Limited
Inexpensive
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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--

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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?

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56 57.3203 Rock Fixtures.

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

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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

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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.

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56 57.3203 Rock Fixtures.

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

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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.

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Roof Bolting
Roof Bolting

• Support Principles
• Support Parameters
• Shotcrete

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Bolting Principles
What is the Bolt System Designed to do?

• Beam building
• Suspension
• Keying
• Surface control - natural arch

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Beam Building
Support Principles
Individual laminations bound together to form a
single beam
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Suspension
Support Principles
Competent Strata
Weak Strata
Suspended layer
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Keying
Support Principles
Fractured Rock
Weak Strata
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Surface Control
Support Principles
Highly jointed, altered or weathered rock
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Bolting Principles

• Beam building
• Suspension
• Keying
• Surface control - natural arch

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Critical Parameters

• Bolt Type
• Strength
• Grade
• Diameter
• Length
• Density (spacing)
• Plate

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Types of Bolts

• Friction Anchored
• Mechanical
• Fully Grouted
• Tensioned Rebar
• Combination/Point Anchored
• Mechanically Anchored/Resin Assisted

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Support Characteristics
Anchorage Clamping Vertical
Stiffness Horizontal Stiffness
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Friction Anchored Support
Splitsets or Swellex Bolts
Split sets provide minimal support (1 ton per
foot of anchorage) when utilized in a suspension
application.
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FRICTION ANCHORED BOLTS
SPLIT TUBE
EXPANDING TUBE
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(No Transcript)
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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
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Split Sets
Inexpensive Easy to Install
No resin cartridges
Can be installed in soft or shifting ground
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SPLITSET
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RADIAL FORCE
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SWELLEX
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DYWIDAG BOLT
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Friction Anchor Bolts
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Critical Parameters

• Bolt Type
• Strength
• Grade
• Diameter
• Length
• Density (spacing)
• Plate

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EXPANSION SHELL ANCHOR BOLT
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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

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PARTS OF A BOLT cont.

• WASHER
• ACTS AS LUBRICATION BETWEEN PLATE AND BOLT
  HEAD

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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

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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
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ROOF BOLT HEAD MARKING
5
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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

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MECHANICAL BOLTS
Plugs
Bail
Shell Leaves
Support Nut
Bolts
BAIL STANDARD
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STANDARD 4 LEAF TYPE EXPANSION SHELL
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THREE PRONG EXPANSION SHELL
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TWO LEAF BAIL TYPE EXPANSION SHELL
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JAM NUT TO STRONG
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• JAM NUT
• TOO STRONG
• ( DOES NOT
• BREAK AWAY
• AND DEFORMS
• THE SHELL )

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DEFORMED SHELL
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JAM NUT TOO WEAK
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• JAM NUT
• TOO WEAK
• ( BREAKS AWAY TOO SOON AND
  DOES NOT EXPAND SHELL )

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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

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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?

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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 gt 125
• HARD PLASTIC

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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

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BOLT STRENGTH
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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
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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.

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FULLY GROUTED BOLTS
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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.

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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.

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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.

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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.

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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.

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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

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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.

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MECHANISMS OF FULLY GROUTED BOLTS
HIGH ANCHORAGE DEVELOPED ALONG BOLT LENGTH
HIGH SHEAR RESITANCE ALONG RESIN/ROCK INTERFACE
LITTLE OR NO SHEAR RESISTANCE ALONG SLIPS AND
JOINTS UNLESS INTERSECTED BY BOLT
LOW PLATE LOADS
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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

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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

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TENSIONED REBAR
Threaded Deformed Bar
Aluminum Plug
Cast Dome
Shear Pin
Tension Nut
TENSION NUTS
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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
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MECHANICAL BOLTS (RESIN ASSISTED)
Compression Tube
Deformed Bar
Mechanical Bolt
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RESIN POINT ANCHOR WITH REBAR SUPPLEMENT
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RESIN POINT ANCHOR WITH STEEL PIPE
SUPPLEMENT
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RESIN POINT ANCHOR WITH SHEAR PIN
COMPRESSION RING
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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
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COMBINATION BOLT
Threaded Deformed Bar
Grout Column
Tensioning Coupler
Shear Pin
Bearing Plate
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WHAT IS A SHEAR PIN ?
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MECHANISMS OF COMBINATION BOLTS
EXTREMELY HIGH ANCHORAGE REGARDLESS OF STRATA
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
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Support Characteristics
Vertical Stiffness
Horizontal Stiffness
Anchorage
Clamping
Bolt Type
Frictional Anchors
Low
Low
Low
Low
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Full Contact Supports
Anchorage Length
Resin Anchored Friction Anchored
(Split Sets, Swellex, Friction Loc)
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Friction Anchor
Resin Anchor
10 Tons Per Foot
1 Ton Per Foot
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Anchorage Variable Along Bolt Length
Anchorage Constant Along The Bolt Length
FULL CONTACT SUPPORT
POINT ANCHORED SUPPORT
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Anchorage 1 Ton/Ft. (10 Tons)
Anchorage 10 Tons
10
FRICTION ANCHORED SUPPORT
(SPLIT SET)
POINT ANCHORED SUPPORT (MECHANICAL BOLT)
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Anchorage 1 Ton/Ft (8 Tons)
Anchorage 10 Tons
8
10
FRICTION ANCHORED SUPPORT
POINT ANCHORED SUPPORT
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1
Anchorage 1 Ton/Ft (1 Ton)
Anchorage 10 Tons
10
FRICTION ANCHORED SUPPORT
POINT ANCHORED SUPPORT
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Critical Parameters

• Bolt Type
• Strength
• Grade
• Diameter
• Length
• Density (spacing)
• Other hardware (plates, washers, straps)

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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.
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Break Time