Post on 06-Jun-2018
Jaco J. van Vuuren
R M TRock Mechanics
Technology
CHIRIMIRI COLLIERYANJAN HILL, 0 SEAM
ROOF SUPPORT REFRESHER COURSE
R M TRock Mechanics
Technology
“Success is not an accident or a miracle.
It is by product of planning, knowledge,
system implementation
and enthusiasm.”
“Success is not an accident or a miracle.
It is by product of planning, knowledge,
system implementation
and enthusiasm.”
TANDSI COLLIERY
R M TRock Mechanics
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Crustal Tectonic Plates of Central Asia R M TRock Mechanics
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A f r i c a nP l a t e
I n d i a
E u r a s i a n P l a t e
Forces Acting on Rock at Depth
H1 H1
V
VR
H2
H2
FORCES ACTING ON ROCK AT DEPTHV= Weight of rock aboveH1 and H2= Tectonic (Horizontal Stress)Vr= Reaction to weight of rock above
R M TRock Mechanics
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BCUkraine4.00,Pullcore.ppt
STRESSES AROUND UNDERGROUND OPENINGSIN – SITU GROUND STRESSES
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STRESSES AROUND UNDERGROUND OPENING
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ROADWAY
EXCAVATION
VERTICAL STRESS CONCENTRATED IN RIBS
HORIZONTAL STRESS CONCENTRATED IN ROOF & FLOORR M TRock Mechanics
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ROADWAY
EXCAVATION
ROADWAY
EXCAVATION
R M TRock Mechanics
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STRESS AROUND A ROADWAY
HORIZONTAL STRESS LOADS THE ROOF AND FLOOR
AFTER EXCAVATION, HORIZONTAL STRESSES CONCENTRATE INTHE STIFF (BRITTLE) BEDS IN THE ROOF AND FLOOR
R M TRock Mechanics
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COAL Roof shear and bulking
Floor heave
HORIZONTAL STRESS
LATERAL SHEAR IN THE STIFF BEDS, KNOWN AS “SOFTENING”,CAUSES THE STRATA TO BULK AND DILATE
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VERTIC
AL STR
ESS
VERTIC
AL STR
ESS
HORIZONTAL STRESS
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R M TRock Mechanics
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AS THE LOWER ROOF BEDS SOFTEN, STRESSES ARE REDISTRIBUTED INTO HIGHER STIFF BEDS
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UNBOLTED ROOF
THIS FAILURE ZONE WILL CONTINUE TO MIGRATEFURTHER INTO THE ROOF
IF NO REINFORCEMENT IS INSTALLED
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UNBOLTED ROOF
EVENTUALLY A LARGE FAILURE ZONE WILL FORM ABOVE EXCAVATION
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UNBOLTED ROOF
IF UNSUPPORTED THIS WILL LEADTO A FALL OF GROUND
FORMING A NATURAL ARCH
R M TRock Mechanics
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UNBOLTED ROOF
IF UNSUPPORTED THIS WILL LEADTO A FALL OF GROUND
FORMING A NATURAL ARCH
• Understand roof failure mechanism
• Using an effective roof support system
• Design by measurement
• Monitor the performance
•Install Roof Control Management System
PRINCIPLES OF RMT
METHODOLOGY ROCKBOLTING
AVERAGE DEPTH 75m ( ranging from 0 to 150m under ANJAN HILL)
CONDITIONS GENERALLY GOOD BUT VARIABLE
WEAK ROOF CONSISTING OF INTERBEDED COAL AND MUDSTONES
PROBLEMS DUE TO WHEATHERING WHERE SEAM OUT CROPS ANDNEAR STRUCTURAL FEATURES SUCH AS SLIPS/JOINTS
ROOF WILL MOVE PRIOR TO A ROOF FALL AND THIS CAN BE USED TO GIVE WARNING OF ROOF FALLS.
HORIZONTAL STRESSES ARE EXPEXTED TO BE LOW IN THE MAIN BODYOF THE SEAM AS IT OUT CROPS AROUND THE FULL CIRCUMFERENCE OF ANJAN HILL & WILL APPROACH ZERO WHERE IT OUT CROPS
SUPPORT POTENTIALLY INADEQUATE FOR DIFFICULT CONDITIONS
CHIRIMIRI COLLIERY, ZERO SEAM
R M TRock Mechanics
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A
B
0
5
01
3
45
2
TWO TYPES OF ROOF FALL HASBEEN OBSERVED TO DATE AT
CHIRIMIRI
- LOW HORIZONTAL STRESS IN CONJUNCTIONWITH INTERSECTING SLIPS/JOINTS
- UNSUPORTED SPANS LEFT STANDING FOR AN EXTENDED PERIOD OF TIME
R M TRock Mechanics
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CHIRIMIRI COLLIERY, ZERO SEAM
Stress
Movement
Key:
Size of arrow denotes magnitude
DIAGRAM SHOWING MECHANISM OF ROOF FAILURE DUETO MINOR CHANGES IN HORIZONTAL SHEARASSOCIATED WITH A PRE-EXISTING SLIPS
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(a) (b)
(c) (d)
(C) (D)
or
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R M TRock Mechanics
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R M TRock Mechanics
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R M TRock Mechanics
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BOLT REINFORCEMENT ENABLES THE IMMEDIATE ROOF TO WITHSTAND HIGHER LOADS
IF SUFFICIENT REINFORCEMENT IS INSTALLEDROOF SOTENING CAN BE MAINTAINED
WITHIN THE BOLTED HEIGHTR M TRock Mechanics
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BOLTED ROADWAY
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QuadbolterR M TRock Mechanics
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Hexagon Drill RodsR M TRock Mechanics
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R M TRock Mechanics
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BOLT & END ASSEMBLY
SHEAR PIN BREAKOUT NUTSSHEAR PIN BREAKOUT NUTS
SHEAR PIN BREAKOUT NUTSSHEAR PIN BREAKOUT NUTS
SHEAR PIN
R M TRock Mechanics
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R M TRock Mechanics
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R M TRock Mechanics
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Components of a steel rockbolt assembly in-situ • Rockbolt• length colour coded ( Min: 2.3m in
roof )• 2.4m• Yield Strength 23t - 26t ; UTS 27t –
31t• Thread strength > 20t
• Domed Washer Plate • Deformable – (14 – 20 Tonne)• Pull Through – (21 – 29 Tonne)
• Conical Seat – 18 degrees • misalignment• Low Friction Washer• Torque Nut - ( 90 – 175Nm )• Resin - Two speed – ( 30 sec & 2 min )• W-Straps / Plates25
18o
Domed washer plate
Rockbolt
Conical seat
Nut
Low Friction WasherW-Strap
R M TRock Mechanics
TechnologyW-STRAP & W-PLATE (Butterfly Plate)
R M TRock Mechanics
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Resin CapsulesR M TRock Mechanics
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Resin CapsulesR M TRock Mechanics
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BASIC PRE-DRILLING CHECKS
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1. Are your drill bits sharp and the right size?
2. Are the drill steels straight with no bends or damaged?
3. Ensure finish steel is the correct length, hole should be approx 100mm shorter than the bolt length..
4. Are you wearing approved eye and hearing protection?
R M TRock Mechanics
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R M TRock Mechanics
TechnologyINSTALLING BOLTS
1 2 3 4 5 6 7 8 9 10 11 12 131 2 3 4 5 6 7 8 9 10 11 12 13 BCUkraine4.00,How.ppt
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R M TRock Mechanics
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BCUkraine4.00,Standards.ppt
Resin NOT pushedTo back of hole
Resin forms sealtrapping air in backof hole.Impossible to spin bolt to back of hole.Nut breaks out too soon.
Resin installed in reverse order
Fast set resin can stall the bolterbefore bolt getsto back of hole.Nut breaks out to soon.
1 2 1 2 1 2
Resin correctlyinstalled to back
of hole
Bolt installedcorrectly
slow set
fast set
fast set
slow set fast set
slow set
BOLTING STANDARDSIMPORTANCE OF CORRECT RESIN INSTALLATION
BCUkraine4.00,How.ppt
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BOLTING STANDARDSTHE IMPORTANCE OF HOLE LENGTH
Hole too long.Resin pushed to back of hole.Not fully encapsulated.
<25mm
>75mm
25 75mm
Hole too short. Full encapsulation.Excess resin spun out of hole.Nut broken out and spun to end of thread.Unable to tension nut / plate to roof.
Hole correct length for bolt.Full encapsulation.No resin lost.Nut broken out and tensioned to roof.
Bolt length
BCUkraine4.00,How.ppt
R M TRock Mechanics
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R M TRock Mechanics
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BOLTING STANDARDSCORRECT EXPOSED THREAD
BCUkraine4.00,How.ppt
<25mm >75mm 25mm - 75mm
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1 2
3 4 5
UNEVEN ROOF
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COMMON ROOFBOLTINSTALLATION PROBLEMS
COMMON ROOFBOLTINSTALLATION PROBLEMS
EXCESSIVE THREADEXCESSIVE THREADR M TRock Mechanics
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HOLE TOO SHORT DRILL HOLE CORRECT LENGTH
RESIN FAULTY CHECK RESIN QUALITY
BOLT TENSIONED TOO SOON
WAIT FOR CORRECT TIME
RESIN NOT MIXED PROPERLY
MIX CORRECTLY
R M TRock Mechanics
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3
Thrust and spinuntil bolt is fully inserted
1
Continue to spinfor the correctperiod of time as specified by therein supplier
4
Correct quantity ofresin inserted to ensure full the back of hole
2
retaining cap
Installationtube
Hold for specified period of time.Resin sets
5 7
TOO MUCHTHREADVISIBLE
6
Break out torquenut and tighten.
INSTALLING A ROOFBOLT IN A SHORT HOLE
Stop on drill rod
Hole ~100mm shorterthan bolt drilled tofixed distance
NO THREAD SHOWING THROUGH NUTNO THREAD SHOWING THROUGH NUTR M TRock Mechanics
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HOLE TOO LONG DRILL HOLE CORRECT LENGTH
RESIN FAULTY CHECK RESIN QUALITY
BOLT NOT TENSIONED
TENSION BOLT CORRECTLY, CHECK MACHINE TORQUE, CHECK BREAKOUT NUTS
R M TRock Mechanics
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3
Thrust and spinuntil bolt is fully inserted
1
Continue to spinfor the correctperiod of time as specified by therein supplier
4
Correct quantity ofresin inserted to ensure full the back of hole
2
retaining cap
Installationtube
Hold for specified period of time.Resin sets
5 7
NOT ENOUGHTHREADVISIBLE
6
Break out nutwill not workproperly.
INSTALLING A ROOFBOLT IN A LONG HOLE
Stop on drill rod
HOLE DRILLEDTOO DEEP
BOLT NOT AT BACK OF HOLE RESIN NOT PROPERLY MIXED
R M TRock Mechanics
TechnologyPLATE NOT TIGHT TO ROOFPLATE NOT TIGHT TO ROOF
BOLT NOT TENSIONED
CHECK MACHINE TORQUE
TENSION BOLT CORRECTLY
CHECK BREAKOUT NUTS
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REPLACEMENT BOLT ADJACENT TO FAILED BOLTREPLACEMENT BOLT ADJACENT TO FAILED BOLT
GOOD PRACTICE
ALWAYS REPLACE FAILED BOLT WITH A PROPERLY INSTALLED BOLT
R M TRock Mechanics
TechnologyROOFBOLTING PROBLEMSROOFBOLTING PROBLEMS
EXCESSIVE THREAD -FAILED BOLT
REPLACEMENT BOLT -GOOD PRACTICE
R M TRock Mechanics
TechnologyROOFBOLTING PROBLEMSROOFBOLTING PROBLEMS
BROKEN BOLTS
REPLACEMENT BOLTS
R M TRock Mechanics
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3
Thrust and spinuntil bolt is fully inserted
Hole ~100mm shorterthan bolt drilled tofixed distance
1
Continue to spinfor the correctperiod of time as specified by therein supplier
4
Correct quantity ofresin inserted to ensure full the back of hole
2
retaining cap
Installationtube
Hold for specified period of time.Resin sets
5 7
Installation complete
6
~ 25mm thread showing
Break out torquenut and tighten.
CORRECT SEQUENCE FOR INSTALLING A ROOFBOLT
Stop on drill rod
EQUIPMENT CONSUMABLES
Drill bits 27mm Twin wing negative rakesharp, not chipped, not blocked
Drill rods 19mm or 22mm HexCorrect lengthStraight not bent“O” rings fittedClear not blocked
Air supply Minimum 80 psi at the M/COil bottle full filter; clean
Water supply 120 psi / 4 gpm
Insertion tubes Correct length = Able to pushresin to back of hole
Resin 450mm red, 800mm green min: perhole (roof). Where extra resin required this to be green
Bolts 2.4m A.T. (roof)
Lagging Options include: W - straps, W-Plates
Dome plates Convex side adjacent sphericalseat; sitting flat in W strap
Torque nuts Break out @roof 90 – 120 Nm (66 – 88 ft lbs)
BCUkraine4.00,Standards.ppt
R M TRock Mechanics
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INSTALLATION SAFETY
Inserting bolts Full thrust low rev spinthrough resin to back of hole.Continue to spin for 5 seconds
Setting time 30 seconds for red resinto set
Torque up Stall machine
Exposed thread Minimum 25mm ; maximum 75mm
Work from under last row of bolts
> Use PPE (personal protective equipment)- ear defenders- eye protection- gloves / clothing
BCUkraine4.00,Standards.ppt
R M TRock Mechanics
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THE ROTARY SINGLE HEIGHT
TELL TALE
THE ROTARY SINGLE HEIGHT
TELL TALE
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R M TRock Mechanics
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TELL TALES ARE SAFETY DEVICES WHICH PROVIDE A CONTINUOUS VISUALINDICATION OF THE LEVEL OF ROOF DEFORMATION THAT HAS TAKEN PLACE WITHIN THE MONITORED HEIGHT FOLLOWING INSTALLATION
THE ROTARY DESIGN HAS BEEN DEVELOPED TO GIVE A RESOLUTION OF 1mm
THIS ACCURACY IS IMPORTANT AT SITES WHERE ROOF DEFORMATIONLEVELS ARE GENERALLY LOW
R M TRock Mechanics
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How a rotary tell tale works
R M TRock Mechanics
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Technology
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R M TRock Mechanics
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R M TRock Mechanics
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ACTION LEVELSACTION LEVELS
GREEN 0 - 5 mm
YELLOW 5 - 10 mm
RED 10 mm +
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ACTIONSACTIONS
GREEN No action required, continue routine monitoring
YELLOW Install additional standard length reinforcement to increase density of support.Install sonic extensometer to identify type andlocation of deformation.To be co-ordinated by Bolting Engineer - RMT
RED Restrict access. Consult Shift Boss / Mine Under Manager/Bolting Engineer - RMT.
GOLDEN RULEGOLDEN RULE
IF YOU SEE ANY TELL TALEIN YELLOW SECTOR
INFORM YOUR SUPERVISOR
IF YOU SEE ANY TELL TALEIN YELLOW SECTOR
INFORM YOUR SUPERVISOR
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GOLDEN RULEGOLDEN RULE
IF YOU SEE ANY TELL TALEIN RED SECTOR
WITHDRAW FROM AREAAND INFORM YOUR
SUPERVISOR
IF YOU SEE ANY TELL TALEIN RED SECTOR
WITHDRAW FROM AREAAND INFORM YOUR
SUPERVISORR M TRock Mechanics
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