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|The failure of yield pillar-based gate mad designs to provide adequate ground control performance is primarily related to the use of "critically" sized chain pillars. A "critical" pillar is one that falls into a range of pillar sizes that are too large to either yield nonviolently or yield before the roof and floor sustain permanent damage, but are too small to support full longwall abutment loads. To directly compare the in-mine performance of critical and yielding pillar designs, the U.S. Bureau of Mines recently completed a field study in a tapering gate road at the Sunnyside No. 1 Mine, Sunnyside, UT. Extreme pillar stresses and associated coal bumps characterize the response to first panel mining of a 16.8-m-wide critical design. Significantly lower pillar stresses, early yielding of the pillar and adjacent panel rib, and an absence of coal bumps suggest that a narrower 12.2-m-wide design more closely approaches proper yield pillar dimensions. Probehole drilling of several 10.6-m-wide pillars revealed low stress levels and substantial pillar and panel rib yielding prior to abutment onset. suggesting a properly functioning yield pillar design.|
Additional chapters/articles from the SME-ICGCM book Proceedings of 14th International Conference on Ground Control in fining
|Truss Systems For Longwall Tailgate Support - Update||Cable Support Systems For Longwall Gate Road Stability||Innovative Tailgate Support For Heavy Ground: 11 Left Longwa||Parameters Affecting Resin-Anchored Cable Bolt Performance:||Roof Support Performance In High Stress Conditions||Regional Horizontal Stress And Its Effect On Longwall Mining||Deformation Development Around Mine Roadways And Simulation||Monitoring Mobile Roof Supports||Analysis Of Retreat Mining Pillar Stability||Planning And Design For Barrier Pillar Recovery Three Case H||Influence Of Partings In A Coal Seam On Long Term Pillar Sta||A Cooperative Study Of Gate Entry Designs Welbeck Colliery (||Comparative Case Study Of Yielding And Critical Coal Pillar||Comparison Of Empirical, Analytical, And Numerical Methods O||Nonlinear Approach For Determining Design Criteria For Yield||In-Situ Coal Strength Determination - Case Studies||The Design And Application Of Propsetter? In Underground Coa||Renewed Interest In Prop Supports As A Replacement For Wood||Improved Intersection Design And Monitoring In The Sydney Co||Drivage System In Retreat Longwall Gateroad||Case Study Of Stability Investigations Related To Shallow Un||Analysis Of Rockbolt Performance At The Waste Isolation Pilo||Continuous Improvement In Cuttable Coal Rib Support In Austr||Floor Failure Induced By Lateral Stress Ahead Of Longwall Su||Towards A Method Of Determining Floor Quality In An Undergro||Chinese And North American High-Extraction Underground Coal||Integration Of CAD-Based Mine Planning And Subsidence Engine||Development Of A Subsidence Database And Determination Of Su||Statistical Regional Calibration Of Subsidence Prediction Mo||Subsidence Monitoring Results, Thick Seam Longwall Mining In||Application Of Mechanical And Groundwater-Flow Models To Pre||The Application Of Underground In-Seam Seismic Methods (UISS||Vertical Stress Redistribution Around A Retreating Longwall||Entry Stability Monitoring & Analysis For Longwall & Continu||A Case Study Of A Deformation Mechanism Around A Two-Entry G||Multiseam Mining On South African Collieries||Design And Planning Of Lower Seam Longwall Gateroads||Optimizing Pillar Design In A Multi-Seam Environment|