3 Introduction to Bolting The principal objective in the design of a roof support system is to help the rock mass create a self-supporting structure. The usage of rock bolts can be combined with wire mesh, shotcrete and concrete lining to cope with different situations encountered during mining or tunneling.
4 Examples of Self Drilling Bolts ?Hilti Sandvik others
5 Problems with Current Rib Bolting Practise Need to drill hole and then retract, hoping the hole does not collapse, install bolt and actuate to tension.Possible need to auger hole.Ability to reach rib with head plate.Safety ( Time spent on operation ).Potential for rib collapse.Manual handling.Mesh alignment.Number of consumables.
6 Introduction to the SDB Bolting Concept Sandvik Self Drilling Bolt (SDB)The objective – To develop a Self Drilling Bolt for UG Soft Rock applications.The project started in Q4/2004 in MGT Newcastle.Use hollow bar to allow flushing during drilling.Mechanical anchoring and post grouting (if needed).Drill, Tension and Grout.
8 Technical AdvantagesSelf Drilling- Installation of the bolt is quicker and simpler when it drills it’s own hole.Strength- axial load capability (stiffness) is increased through the combined use of a mechanical anchor plus full encapsulation with either thixotropic or cementatious grout.Pretension- as the bolt is pre-tensioned by use of the mechanical anchor, the rib layers are forced together before the injection of the grout. Standard chemical capsules can be forced into cracks and fissures under the hydraulic pressure created when the bolt is inserted which results in separations being held open and a loss in encapsulation.
9 Rib Bolt Data Sheet Hollow bar OD = 19mm, ID = 9.5mm Bolt DescriptionHollow bar OD = 19mm, ID = 9.5mmFrazer & Jones D10L Expansion ShellNut (M20 LH) with shear pin, 36AF (optional non-shear pin for no tail bolt)Bolt length: typically 1.2m (any length can be supplied)Plate: Special SDB Butterfly AssemblyPlain Hollow BarTypicalTensile Strength (kN)Yield Strength (kN)Standard Elongation (50mm) (%)Bar Shear Strength (kN)
10 Installation Procedure Insert self drilling rib bolt in drill chuck.Drill 36mm diameter hole in rib using SD Bolt & RH rotation on rig.On completion of drilling, anchor bolt by using reverse rotation on drill motor to set expansion shell and tension bolt.
12 Trials to Date Drill trials at Mandalong, West Wallsend and Beltana trialling steel drill bit designBolt trials at West Wallsend and Manneringtrialling old style self drilling boltSD Bolt trials at Mandalongcurrent design and trials
13 Pull Test – D10L Anchor in Coal West Wallsend - 10, 10, 12, 8, 13, 13, 12.5, 9.5, 9.5, 16 tonneMannering - 16 tonneclick on photo to play pull test video
14 Grouting Recommendations/Options Rib bolt has threaded hollow centre bar allowing easy coupling of grout pump and straight clear grouting passage through centre of tube.Initial contacts with Specialist Site Services, with regards to post grouting the SD Bolt, have indicated no foreseeable problems.Currently organising trials with BASF, developing grout and resin compositions.Grout trial with solid bolt design proved feasibility of grouting, and new hollow bolt design should better suit grouting.
15 Engineering Changes to Miner/Drill Rig Triple stage bolting rig.SDB chuck, extension dolly.Reverse rotation controls.Pressure control on reverse rotation (95 bar = 200Nm on ME10).
16 Hazard Study & Risk Assessment A Hazard Study and Risk Assessment for the Installation Procedure of the Sandvik Self Drilling Rib Bolt, has been developed in conjunction with Mandalong Colliery.Also a pull test SOP has been done. ( West Wallsend, Mandalong Colliery ).Could use these documents as templates for your colliery.Will conduct a separate study to your requirements if needed.
17 Customer Implementation Process Step 1 – Customer request, initial presentation and meetingRecord feedback and interestStep 2 – UG survey of equipment and current practiseView and measure continuous miner, drill rigs and clearances, understand the engineering issues of what will impact on the installation procedureStep 3 – Final proposal presentation to mineFully engineered and costed proposal back to mine
18 Value Proposition for Customers and Sandvik Improved safety – operator is exposed 50% less time, reducing risk.Improved productivity – drivage rates will improve due to time savings.Reduced bolting costs – bolting cycle time is reduced lower total costs.Ability to automate – use of only one consumable, eases automation task compared with current three consumable practise (rod, sausage and bolt).More choices and competition.Improved maintenance outcomes – halves movements on drill rig.Sandvik:New opportunity in more stable consumable business.Sandvik seen as a solution provider for rapid roadway and mine development.Increased customer process focus.
19 Future Developments Roof SD Bolt. Cuttable Rib SD Bolt. Continue to develop bolt.Future automation.Total system solution.