How megabolts installed as primary support assist in
How megabolts installed as primary support assist in safely improving development rates ACARP Roadway Development Operators Workshops - October 2011
Introduction Three types of megabolts installed from continuous miner Post grouted megastrands – MW 9 ● Resin anchored, torque‐tensioned megaflex bolts ‐ TTX ● Resin anchored, post groutable fibreglass rib bolts ● ACARP Roadway Development Operators Workshops - October 2011 2
MW 9 Megabolt Most commonly installed megabolt is the barrel & wedge version – MW 9 ● 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
MW 9 – Nth Goonyella face road ACARP Roadway Development Operators Workshops - October 2011 4
MW 9 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
MW 9 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 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
MW 9 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
MW 9 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
MW 9 developments Mechanised insertion ● Lobster from Conway Engineering ● Being used at Angus Place ● Favourable reports so far ACARP Roadway Development Operators Workshop 2011 10
MW 9 developments Resin grouting using Minova Carbothix ● Immediate roof support ● Remote pumping ● Quicker grouting ACARP Roadway Development Operators Workshop 2011 11
Megaflex 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 – advantages No exposure to high pressure tensioner hydraulics ● Reduced injuries from handling tensioners ● Quicker installation than hydraulically tensioned cables ● Combo dolly ● ACARP Roadway Development Operators Workshops - October 2011 13
Combo dolly – no changing dollies Mixing Tightening Inner socket engages hex drive Outer socket engages nut ACARP Roadway Development Operators Workshops - October 2011 14
TTX – 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 – 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 – 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 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 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 ACARP Roadway Development Operators Workshops - October 2011 19
Groutable 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 ACARP Roadway Development Operators Workshops - October 2011 20
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