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|The selection of tensioned versus non-tensioned roof bolts, for primary coal mine roof support, has been debated for well over 25 years. The wide spread use of fully grouted rebar marked the beginning of the discussion of the relative importance of bolt tension and the resultant immediate roof compression. The focus is on roof conditions encountered in coal mines however the discussion may be extended to hard rock mines as well. The theoretical bases for both systems are presented, with the analysis focused on the bolt's ability to actually fulfill the theoretical assumptions. Of specific concern are assumptions about bolt tension upon installation and the likelihood of maintaining useful bolt tension over time. The usefulness of tension roof bolting is limited by the mechanical interaction of roof bolt assembly and the rock, which may be valid at the time of installation only. Ambient mine atmosphere and fluctuation in moisture content changes the physical condition of rock, which may have a significant impact on the effectiveness and longevity of bolt tension. Changes in the material properties of the surface of the immediate roof can invalidate the assumptions, which were made in the design stage of roof support system. This means that the roof support in the long term excavations may be inadequate requiring costly rehabilitation. The presented arguments are illustrated with the examples of some relevant experimental data. Tension primary roof bolting is recommended where the immediate roof is: ? Stiff with a high modulus of elasticity ? Surface layers are continuous and fairly thin ? Not easily weathered|
Additional chapters/articles from the SME-ICGCM book 23rd International Conference on Ground Control in Mining (ICGCM) 23rd
|Geomechanical Criteria of Longwall Face Support Selection at||Rock Fracture, Caving and Interaction of Face Supports Under||Effect of the Approaching Longwall Faces on Barrier and Entr||Computer Simulation of Ground Behaviour and Rock Bolt Intera||lnterpanel Barriers for Deep Western U.S. Longwall Mining||Application of Yieldable and Cuttable Pump Crib in Longwall||Field Testing of a Real Time Roof Mapping Drilling Display S||Problems in "Void" Detection in Coal Mine Water Hazards||Violent Coal Pillar Collapse -A Case Study||Stooping Low Safety Factor Pillars at Goedehoop Colliery - 1||Laboratory Strength Testing of Coal from Selected Illinois S||Downhole Overcoring Stress Measurement at a Western Undergro||Effect of In Situ Stresses on the Stability of Coal Mine Dev||SOMA: A New Method to Calculate the Operative Stress Field:||Numerical Modeling for Increased Understanding of the Behavi||Evaluation of Rockburst Hazard from Core Testing||Investigation of Electromagnetic Emissions in a Deep Undergr||Development and Application of Geotechnical and Rockmechanic||Laboratory Testing of Rib Straps||The New Two-Dimension LaModel Program||Risk Assessment: Multiseam - Single Seam Mining||A Method To Determine Expander Spacing For Steel Pipelines I||A Case Study Of Abandoned Mine Subsidence At Dominion, Nova||Spatial Trends In Rock Strength - Can They Be Determined Fro||Development And Demonstration Of An Alternate Mining Geometr||Evaluation Of Polyurethane Injection For Beltway Roof Stabil||Application Of Ground Penetrating Radar To Evaluate The Exte||A Risk Assessment Tool For Open Cast Mining In South Africa||Analysis Of Practical Ground Control Issues In Highwall Mini||Preventing Falls Of Ground In Coal Mines With Exceptionally||Geo-Mechanical Property And Failures Of Weak Roof Shales In||Eclipse System Bolting In The Illinois Basin||Variation In The Load Transfer Of Fully Encapsulated Rockbol||Bolt Load Changes During Initial Face Advance And Cross-Cut||Coal Mine Primary Support Selection: Tension Versus Non Tens||Improving Stope Support At Modikwa Platinum Mine||3D FEM Simulation For Fully Grouted Bolts||An Investigation Into The Effectiveness Of Support Systems C||Hydraulic Prestressing Units: An Innovation In Roof Support||Improving Roof Truss Performance||Coal Combustion Byproducts-Based Artificial Mine Supports -||The Influence Of Horizontal Stress On Pillar Design And Mine||Investigation Of Pillar-Roof Contact Failure In Northern App||Mapping Hazards With Microseismic Technology To Anticipate R||Practical Detection Of Underground Mine Roof Failure||Heat-Imaging Experimental Study Of Reducing Local Gas Accumu||Microcirculation Theory Analysis Of Spontaneous Combustion O|