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|The U.S. Bureau of Mines and Cyprus Shoshone Coal Corp. conducted a study of deformation mechanisms around a longwall gate-road system in an underground coal mine. Of particular interest was roof deformation over the headgate entry. The strata above and below the coal seam are very weak, carbonaceous mudstones that have planes of weakness oriented along the bedding. Visual observations of previous gate roads over several years suggested that deformation was time dependent and resulted in creep along joints or crack growth. Instruments were installed at a test site to measure deformation around the entry, strew changes in the pillar, and loads transferred to support systems. Multipoint extensometers, instrumented bolts, instrumented trusses, biaxial stressmeters, borehole pressure cells, and single-point extensometers were installed. Monitoring continued until the longwall face passed the test site by 38.7 m (127 ft). Results show that fracture zones arched over the entry from both ribs, most bolts and trusses were loaded past their yield point, and the largest change in secondary principal stress was almost horizontal in the pillar. Displacement measurements in the roof showed classic primary creep.|
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|