Jaco J. van Vuuren

R M TRock Mechanics

Technology

CHIRIMIRI COLLIERYANJAN HILL, 0 SEAM

ROOF SUPPORT REFRESHER COURSE

R M TRock Mechanics

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“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

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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

R M TRock Mechanics

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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

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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

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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

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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

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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)

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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

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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

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How a rotary tell tale works

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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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