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How megabolts installed as primary support assist in safely improving development rates ACARP Roadway Development Operators Workshops - October 2011.

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Presentation on theme: "How megabolts installed as primary support assist in safely improving development rates ACARP Roadway Development Operators Workshops - October 2011."— Presentation transcript:

1 How megabolts installed as primary support assist in safely improving development rates ACARP Roadway Development Operators Workshops - October 2011

2 Introduction 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

3 MW9 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

4 MW9 – Nth Goonyella face road ACARP Roadway Development Operators Workshops - October

5 MW9 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

6 MW9 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

7 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 tonnes ACARP Roadway Development Operators Workshop

8 MW9 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

9 MW9 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

10 MW9 developments Mechanised insertion ● Lobster from Conway Engineering ● Being used at Angus Place ● Favourable reports so far ACARP Roadway Development Operators Workshop

11 MW9 developments Resin grouting using Minova Carbothix ● Immediate roof support ● Remote pumping ● Quicker grouting ACARP Roadway Development Operators Workshop

12 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

13 TTX – advantages ● No exposure to high pressure tensioner hydraulics ● Reduced injuries from handling tensioners ● Quicker installation than hydraulically tensioned cables ● Combo dolly 13 ACARP Roadway Development Operators Workshops - October 2011

14 Combo dolly – no changing dollies Mixing Inner socket engages hex drive 14 ACARP Roadway Development Operators Workshops - October 2011 Tightening Outer socket engages nut

15 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

16 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

17 TTX – advantages ● Increased load transfer from spiral wire ● Groutable version being developed – will require 42 mm dia. hole ACARP Roadway Development Operators Workshop

18 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

19 Groutable FG rib bolt ● 42 t capacity ● Cuttable ● 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 19 ACARP Roadway Development Operators Workshops - October 2011

20 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 20 ACARP Roadway Development Operators Workshops - October 2011


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