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|Pillar recovery continues to be one of the more hazardous activities in underground coal mining. Safety requires that the roof above the intersection remain stable until after the pillar has been extracted. Artificial supports (timbers and Mobile Roof Supports) arc essential to roof stability, but so is the final remnant stump or pushout. Traditional mining practices usually called for the complete extraction of the final stump, but the recent trend (both in the U.S. and internationally) seems to be towards mining plans that leave a remnant stump. For this study, a sample of roof control plans from the Mine Health and Safety Administration (MSHA) Coal Districts were analyzed to determine current pillar recovery practices. Both full- and partial- extraction plans were included. Special attention was paid to whether plans require that a final stump be left, and whether requirements regarding the dimensions of the remnant stump are included. Foreign experience with final stumps is also summarized. It seems that the risk of major pillar falls can often be reduced by leaving final stumps that are large enough to protect the intersection, but small enough that they do not inhibit the caving of the gob. Because final stumps are often irregular in shape, a new approach for estimating their strength is described. Analyses were conducted to assess the effect of seam height and depth of cover on the potential variation in the size of remnant stumps.|
Additional chapters/articles from the SME-ICGCM book Proceedings 20th International Conference On Ground Control In Mining
|Hydraulic Fracturing Of Sandstone And Longwall Roof Control||Status Of Longwall Research In CSIRO||Longwall Moves At Twentymile Recovery Mesh System||Risk Assessment Of Geotechnical Factors Associated With Unde||Load And Deflection Response Of Ventilation Stoppings To Lon||The Stress And Failure Paths Followed By Coal Mine Roofs Dur||Simulated Materials Modeling And Analysis Of The Overburden||Sizing Of Final Stumps For Safer Pillar Extraction||Evaluation Of Mobile Roof Support Technologies||FDM Prediction Of A Yield Pillar Performance In Conjunction||Extraction Ratio In Thin Seams Assuring No Surface Subsidenc||Improving Roof Control At A South African Coal Mine||In-Situ Investigation Into The Causes Of Falls Of Roof In So||Failure Characteristics Of Roof Falls At An Underground Ston||Determination Of Limitation Of Roof Layer Separation (LRLS)||The Integration Of Geology And Engineering In Ground Control||Worldwide Implementation Of Continuous Miner System - Integr||Effect Of Face Advance Rates On The Characteristics Of Subsi||The Response Of A High Order Stream To Shallow Cover Longwal||SDPS For Windows: An Integrated Approach To Ground Deformati||Development Of A Remote Reading Dual-Height Telltale System||Enhanced Surface Control For Roof And Rib Support||Long Term Stability Of Mine Workings In Soft Floor Environme||Visualization Of Geostructure By Mechanical Data Logging Of||A Step Towards Understanding The Behaviour Of Wider Roadways||Research And Application Of Combined Reinforcement System||Estimation Of In-Situ Stress At Ikeshima Colliery Using AE A||Typical Complete Stress-Strain Curves Of Coal||Analysis Of Roof Bolt Systems||Effects Of Bedding Plane Sliding And Separation And Tensione||Systems Used In Coal Mining Development In Long Tendon Reinf||Determination And IT-Supported Evaluation Of Rock Mechanical||Tensioned Cable Bolts As Primary Support: Update||Determination Of Basis For The Double Use Of Rectangular Roc||Cost Preventive System To Control Unstable Roof In Main Line||Injection Techniques for Cost-effective Stabilization of Bri||An Analysis of Rock Failure Around a Deep Longwall Using Mic||Numerical Simulation on Microseismicity Due to Mining at One||Investigation of Seismicity Near Appin, NSW, and its Associa||Effects of Bolt Spacing, Bolt Length, and Roof Span on Bolt||Evaluation of Instrumented Cable and Rebar Bolts as Ground S||Application of the Coal Mining Roof Rating System in South A||Roof Instability Rating (RIR) System and Its Application at||Updating the NlOSH Support Technology Optimization Program (||Mistakes, Misconceptions, and Key Points Regarding Secondary||Non-Destructive Testing on Fully Grouted Rockbolts||Visual Recognition of the Load of Roof-Bolts by an Indicator||A New Rockbolt Axial Load Measuring Device||A New Approach to the Integrity Testing of Ground Anchorages||A Lineament Analysis Case Study of the Fola Coal Co., LLC. N||Analyses of Valley Fill Slope Stability - Three Case Studies||Modeling of Joint and Fracture Distributions in Rock Mass Be|