how megabolts installed as primary support assist in safely improving development rates acarp...
TRANSCRIPT
How megabolts installed as primary support assist in
safely improving development rates
ACARP Roadway Development Operators Workshops - October 2011
IntroductionIntroduction
Three types of megabolts installed from continuous miner
● Post grouted megastrands – MW9● Resin anchored, torque-tensioned megaflex bolts - TTX● Resin anchored, post groutable fibreglass rib bolts
ACARP Roadway Development Operators Workshops - October 2011 2
MW9 MegaboltMW9 Megabolt
● Most commonly installed megabolt is the barrel & wedge version – MW9
● Fully bulbed using spiral rib wire for max load transfer
● Up to 11 m long cables installed from miner in LW installation roads
ACARP Roadway Development Operators Workshops - October 2011 3
MW9 – Nth Goonyella face roadMW9 – Nth Goonyella face road
ACARP Roadway Development Operators Workshops - October 2011 4
MW9 advantagesMW9 advantages
● 42 mm hole – no reaming● Single 1,000 mm resin capsule
with resin retainer● Resin pushed up hole with bolt
– no conduit● Collar fittings attached after
bolt installed● No bearing plate or bolt head to
catch on walkway
ACARP Roadway Development Operators Workshop 2011 5
MW9 advantagesMW9 advantages
● Tension within 5 mins of installation
● Tension using system hydraulics or intensifier
● 9 to 20 t pre-tension can be achieved depending whether system hydraulics or intensifier used
● No air needed on miner● Provides immediate point
anchor support of 57 t
ACARP Roadway Development Operators Workshop 2011 6
Important considerationsImportant considerations
● Bolt is point anchored until grouted
● Anchor length designed to take capacity of bolt – depends on rock type at anchor horizon
● Pull tests must be done to determine if anchor can take full capacity of bolt
● This ungrouted bolt is loaded to 45-50 tonnes
ACARP Roadway Development Operators Workshop 2011 7
MW9 groutingMW9 grouting
● Top down grouted using grout lance – quickest grouting method
● Grouting done within designated time or distance advanced – depends on conditions
● Heavy conditions may require grouting within 24 hrs
● Good conditions (intersections) can be left for more than a week
ACARP Roadway Development Operators Workshop 2011 8
MW9 groutingMW9 grouting
● Grout generally reaches sufficient strength (30 to 40 MPa) within 24 hrs
● Readily & easily audited● Regular auditing has greatly
improved quality of installation
● Grouting non-compliance now less than 5%
● Good installation reduces likelihood of remedial roof support
ACARP Roadway Development Operators Workshop 2011 9
MW9 developmentsMW9 developments
Mechanised insertion ●Lobster from Conway Engineering●Being used at Angus Place●Favourable reports so far
ACARP Roadway Development Operators Workshop 2011 10
MW9 developmentsMW9 developments
Resin grouting using Minova Carbothix●Immediate roof support●Remote pumping●Quicker grouting
ACARP Roadway Development Operators Workshop 2011 11
Megaflex TTXMegaflex TTX
● Torque-tensioned● TT bolt becoming more in
demand● 56 t and 48 t versions● 56 t generally requires 28
mm hole● 48 t a 27 mm hole
ACARP Roadway Development Operators Workshop 2011 12
TTX – advantagesTTX – advantages
● No exposure to high pressure tensioner hydraulics
● Reduced injuries from handling tensioners
● Quicker installation than hydraulically tensioned cables
● Combo dolly
13ACARP Roadway Development Operators Workshops - October 2011
Combo dolly – no changing dolliesCombo dolly – no changing dollies
MixingInner socket engages hex drive
14ACARP Roadway Development Operators Workshops - October 2011
TighteningOuter socket engages nut
TTX – advantagesTTX – advantages
● Roller race between nut & washer reduces friction
● Race is shrouded to keep bearing free of dirt or mud
● 7 t bolt tension from 320 Nm drill torque
● Minimal protrusion from roof – important in low seams
● Removing hex drive reduces protrusion further – as little as 115 mm
ACARP Roadway Development Operators Workshop 2011 15
TTX – advantagesTTX – advantages
● Wires are anchored in the bolt head using button heads forged on end of each wire – maintains max collar strength
● B&W anchor typically reduces cable collar capacity by approx 10%
ACARP Roadway Development Operators Workshop 2011 16
TTX – advantagesTTX – advantages
● Increased load transfer from spiral wire
● Groutable version being developed – will require 42 mm dia. hole
ACARP Roadway Development Operators Workshop 2011 17
Limitations of torque-tensioned cablesLimitations of torque-tensioned cables
● Reduced bolt pre-tension compared to hydraulic tensioning
● Possible use of torque multipliers
‐ Slows down installation
‐ Failure of torque multiplier can delay production
‐ Possible safety issues● May need modifications to head-plate of drill mast to
accommodate bolt and/or dolly ● Full resin encapsulation difficult for cables > 4 m● Load transfer lower than for bulbed cables● If bulbed then larger hole dia. & bigger resin capsule
ACARP Roadway Development Operators Workshop 2011 18
Groutable FG rib boltGroutable FG rib bolt
● 42 t capacity● Cuttable● 42-45 mm drill hole● Point anchored initially● Breakout nut● High torsion strength –
stalls rib bolting rigs● 17 t collar capacity● Shear strength of 14 t● SG of 1.9 to 2.1 – separates
in washery
19ACARP Roadway Development Operators Workshops - October 2011
Groutable FG rib dowel - advantagesGroutable FG rib dowel - advantages
● Immediate rib support● Hollow centre - post groutable
with thixotropic grout● Full encapsulation vital in
heavy rib conditions ● Easily audited● No secondary rib support
required – maximises development rates
20ACARP Roadway Development Operators Workshops - October 2011