How megabolts installed as primary support assist in safely improving development rates

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 2011

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 2011

4. MW9 – Nth Goonyella face road ACARP Roadway Development Operators Workshops - October 2011

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 2011

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 2011

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 45-50 tonnes ACARP Roadway Development Operators Workshop 2011

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 2011

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 2011

10. MW9 developments Mechanised insertion • Lobster from Conway Engineering • Being used at Angus Place • Favourable reports so far ACARP Roadway Development Operators Workshop 2011

11. MW9 developments Resin grouting using Minova Carbothix • Immediate roof support • Remote pumping • Quicker grouting ACARP Roadway Development Operators Workshop 2011

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 2011

13. 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

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

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 2011

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 2011

17. TTX – advantages • Increased load transfer from spiral wire • Groutable version being developed – will require 42 mm dia. hole ACARP Roadway Development Operators Workshop 2011

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 2011

19. 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

20. Groutable FGrib 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