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|One of the critical variables affecting resin bolt performance is the size of the resin annulus, defined as the difference between the hole and bolt radius. The vast majority of the millions of resin roof bolts installed each year in the United States employ an annulus between 0.125 and 0.188 inch. As the annulus size decreases the resin flow around the bolt becomes more difficult, increasing the resin pressure induced by bolt insertion. As the resin pressure increases the loss of resin into bedding planes and vertical fractures in the rock increases. As the annulus size increases the mixing of the resin paste and mastic becomes less efficient. Thus, the lower and upper limits of the optimum annulus size is determined by insertion pressure and mixing considerations, respectively. Previous U.S. Bureau of Mines researchers have concluded that a 0 125 inch annulus is optimal. However, others have recently reported that a 0.095 inch annulus with special rolled deformation (SRO) bolts provide superior anchorage to standard rebar with a very large 0.250 inch annulus, attributing SRD resin loss in weak ground to oversized holes. The effect of annulus size on unit length pull strength and resin loss to fractured rock was investigated. Short encapsulation pull tests with resin annuluses of 0.125 and 0.095 inch resisted an average of 2.25 tons per grouted inch, with no significant variation. However, annulus size has shown a dramatic effect on the magnitude of resin lost to simulated rock fractures. No. 5 standard . No. 6 standard, and No 7 J-Bar rebar were inserted into two different viscosity resin cartridges designed for 4 foot boll encapsulation into a one inch inside diameter metal tube, To simulate a rock fracture, a 0.250 inch diameter orifice was located near the capped end of the tube Resin loses increased as annulus size decreased, with a minimum loss of 35% and a maximum loss of 60% associated with 0.125 and 0.095 inch annuluses, respectively.|
Additional chapters/articles from the SME-ICGCM book Proceedings - 18th International Conference on Ground Control in Mining
|Pillar Collapse at Welgedacht Colliery, South Africa: A Case||Causes of Massive Directional Roof Falls in Room and Pillar||Catastrophic Collapse Of Highwall Web Pillars And Preventati||Mine Panel Collapse - Two Case Studies||Roof Geology Mapping In Underground Coal Mines||Electromagnetic Seam Wave Mapping Of Roof Rock Conditions Ac||Geological Conditions At Continuous Miner Sections; Examples||The Role Of Engineering And Geology In Analyzing Ground Cont||The Development And Use Of Risk Assessment Techniques To Ass||Time-Dependent Analysis Of Underground Opening Stability||Tekflex As A Sprayon Screen Replacement In An Underground Ha||Tunnel Deformation Monitoring "Action Levels" In Coal Mines||Skin Failure Of Roof And Rib In Underground Coal Mines||Application Of Polyurethane Injection For Rehabilitation Of||Design Considerations For Bump-Prone Longwall Mines||Design Methodology For Standing Secondary Roof Support In Lo||Modern Shield Technology: Better Than Ever But Still Not Per||Shield Monitoring To Forecast Severe Face Weightings At The||Monitoring Of Longwall Seal Behaviour For Permeability And S||Ground Control In South African Coal Mines - A U.S. Perspect||Rock Mechanics Issues In The Trona Patch||Highwall Augering In Ultra-Thick Western Coal Reserves: Uniq||Seismic Events Due To Underground Mining Activities||Control Technology For Roof Drill Operators||Resin Annulus Size Effects On Rebar Bolt Pull Strength And R||Roof Bolt Response To Shear Stress: Laboratory Analysis||Laboratory Study Of Shear Loading And Bolt Load Transfer Mec||Analysis Of Cable Bolt Performance Using Numerical Modeling||Roof Bolting Application In Longwall Mining In Indonesia And||Ground Control Design For Multiple Seam Mining Using Finite||Pillar Design Issues For Underground Stone Mines||Calibration Of The Analysis Of Longwall Pillar Stability (AL||Mine Convergence When Using Mobile Roof Supports In Pillar R||The Advance And Relieve Mining Method: A Horizontal Stress C||Localized Horizontal Stress And Its Effect On Ground Control||Prediction And Control Of Surface Subsidence Over Abandoned||Effects Of Mining On Underground Infrastructures In The Germ||Ground Deformation In The Case Of Underground Mining Of Thic||Prevention Of Time-Dependent Subsidence By Elimination Of Gr|