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|Mines with exceptionally low-strength roof (UCS <3,500 psi and CMRR <40) are much more likely to struggle with roof falls than other mines. Weak-roof is a particular problem for many room and pillar mines in the Midwestern and Northern Appalachian coal basins. Traditional roof support techniques are often not up to the challenge at these operations. This paper focuses on two mines, one operating in the Upper Freeport seam and the other in the Herrin No. 6 seam. Together, the two mines had more than 300 roof falls during a recent 5 year period. Each has experimented with a variety of roof bolt types and lengths, and with different supplemental supports. Detailed statistical analysis was conducted to determine which support combinations have proven to be most effective. Geology, horizontal stress, and time are also important at both mines. Successful control techniques have included; ? Identifying particularly troublesome lithologic roof units; ? Installing longer and stronger roof bolts; ? Installing supplemental support in intersections, and; ? Limiting the duration that a panel remains open. The lessons learned from these mines, and others like them, could help improve ground control safety for the entire U.S. mining industry.|
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|