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. Scaling Hand verses Mechanical Scaling Scaling Bar Mechanical Scaler
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 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 Scaling Shotcrete Rock Bolt Installation More versatile Costly Limited
Inexpensive 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 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 Fixtures. (2) Make this certification available to an authorized representative of the Secretary.
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 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 Fixtures.
(c) Bearing plates shall be used with fixtures when necessary for effective ground support. 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 Support Principles Support Parameters Shotcrete
Bolting Principles What is the Bolt System Designed to do? Beam building Suspension
Keying Surface control - natural arch Beam Building Support Principles Laminated Weak Strata
Strata Individual laminations bound together to form a single beam Suspension Competent Strata Weak
Strata Support Principles Anchorage Zone Suspended layer Keying Fractured
Rock Weak Strata Support Principles Surface Control Support Principles
Highly jointed, altered or weathered rock Bolting Principles Beam building
Suspension Keying Surface control - natural arch Critical Parameters Bolt Type Strength Grade Diameter Length
* Clamping * Vertical Stiffness * Horizontal Stiffness Friction Anchored Support Splitsets or Swellex Bolts Split sets provide minimal support (~1 ton per foot of anchorage) when utilized in a suspension application.
FRICTION ANCHORED BOLTS SPLIT TUBE EXPANDING TUBE MECHANISMS OF FRICTION ANCHOR BOLTS LOW ANCHORAGE DEVELOPED ALONG
BOLT LENGTH NO CLAMP LOADS LITTLE OR NO SHEAR RESISTANCE ALONG SLIPS AND JOINTS UNLESS INTERSECTED BY BOLT
LOW PLATE LOADS Split Sets Inexpensive Easy to Install No resin cartridges Can be installed in soft or shifting ground SPLITSET
RADIAL FORCE SWELLEX DYWIDAG BOLT Friction Anchor Bolts Critical Parameters
Bolt 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
5/8 INCH DIAMETER 5 Grade 55 ROOF BOLT MARKINGS GRADE
40 55 60 75 100 DIAMETER DESIGNATION 3/4 INCH UP NONE
5/8 INCH UP 5/8 INCH UP 5/8 INCH UP X 5/8 INCH UP Plugs Bail Shell Leaves Support Nut
Bolts BAIL STANDARD STANDARD 4 LEAF TYPE EXPANSION SHELL
THREE PRONG EXPANSION SHELL TWO LEAF BAIL TYPE EXPANSION SHELL JAM NUT TO STRONG JAM NUT
TOO STRONG ( DOES NOT BREAK AWAY AND DEFORMS THE SHELL ) DEFORMED SHELL JAM NUT
TOO WEAK JAM NUT TOO WEAK ( BREAKS AWAY TOO SOON AND DOES NOT EXPAND SHELL )
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 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 ? 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 STRENGTH BOLT DIA & GRADE
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 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. 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 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 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 BOLTS HIGH ANCHORAGE DEVELOPED ALONG
BOLT LENGTH HIGH SHEAR RESITANCE ALONG RESIN/ROCK INTERFACE NO CLAMP LOADS LITTLE OR NO SHEAR RESISTANCE ALONG SLIPS AND JOINTS
UNLESS INTERSECTED BY BOLT LOW PLATE LOADS 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 Threaded Deformed Bar Cast Dome Shear Pin
TENSION NUTS Tension Nut MECHANISMS OF TENSIONED REBAR BOLTS EXTREMELY HIGH ANCHORAGE REGARDLESS OF STRATA VERY HIGH CLAMP LOADS
HIGH SHEAR RESISTANCE ALONG RESIN/ROCK INTERFACE CLAMP LOAD DEVELOPS VERY HIGH SHEAR RESISTANCE ALONG SLIPS AND JOINTS VERY HIGH PLATE LOADS
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 MECHANISMS OF POINT RESIN ANCHORED BOLTS
HIGH ANCHORAGE EVEN IN SOFT ROCK HIGH CLAMP LOADS CLAMP LOADS DEVELOP MODERATE SHEAR
RESISTANCE ALONG BEDDING PLANES,SLIPS AND JOINTS HIGH PLATE LOADS Threaded Deformed Bar Grout
Column Tensioning Coupler Bearing Plate Shear Pin WHAT IS A SHEAR PIN ?
MECHANISMS OF COMBINATION BOLTS EXTREMELY HIGH ANCHORAGE REGARDLESS OF STRATA VERY HIGH CLAMP LOADS
GROUTED LENGTH REINFORCES THE STRATA LIKE A FULLY GROUTED BOLT CLAMP LOADS DEVELOPS HIGH SHEAR RESISTANCE ALONG BEDDING PLANES, SLIPS AND JOINTS VERY HIGH PLATE LOADS
Support Characteristics Bolt Type Anchorage Clamping Vertical Stiffness
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