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|Extensive measurements and underground observations in three Western U. S. coal mines are integrated in this paper to determine in-situ pillar load-deformation characteristics for narrow (30 it wide, 80 ft long) pillars in two-entry gate road systems. In spite of similarities in the regional geology, coal pillar laboratory mechanical properties and gate pillar geometries, the pillar peak strength, post-failure behavior, and failure mechanism were shown to be significantly different. Pillar peak strength was shown to be dependent on depth at one site, approaching burst-prone stress levels of 4000 psi. At another site, the pillar peak strength was lower because of lower confinement; this was related to the higher frequency of cleats and the lower friction- al properties of the roof/floor and coal contact. Two failure mechanisms were identified - one in the pillar, and the other in the mine floor. The roof stability was good at all three sites because of the thick-bedded nature of the roof strata and limited total gate span in a two-entry system. Existing pillar design techniques were shown to be inadequate for design, requiring adjustments for depth of cover, cleat frequency, and roof /floor frictional properties.|
Additional chapters/articles from the SME-ICGCM book Proceedings 7th International Conference on Ground Control in Mining (ICGCM) 7th
|Field Evaluation of Yield Pillar System at a Kentucky longwa||In-Situ Pillar Strength Determination for Two-Entry Longwall||Integrity Factor Approach to Assess the Stability of Room-an||Longwall Recovery Utilizing The Open Entry Method And Variou||Design Of Lower Seam Longwall Operations In Multiple Seam Mi||Method Of Selecting Suitable Types Of Powered Supports At Lo||An Overview Of The National Roof Evaluation Accident Prevent||Strata Control Advances At Jim Walter Resources, Mining Divi||Portal Stability In Rock||Bailey Mine Slurry Impoundment Longwall Subsidence Monitorin||Prediction Of Surface Subsidence And Strain In The Appalachi||Computerised Subsidence And Displacement Prediction Using In||Computer Modeling Of Yield Pillar Behavior Using Post-Failur||Practical Rock Mechanics For Safety And Productivity Improve||Geotechnical Mine Design Of The Foidel Creek Mine||A Hydrogeomechanical Study Of Overburden Aquifer Response To||Comparison Of Predictions And Measurements Of Subsidence Cau||RYBAD Empirical Field Model For Prediction Of Maximum Land S||Mining Under Strong Roof||Sub-Surface Ground Movements Associated With Longwall Mining||A Computer Simulation Of Breakage Of The Main Roof In Longwa||Evaluation Of Low-Coal ATRS Systems||Analysis Of Major Failure Through Integration Of Static And||Outbursts And Rockbursts In Coal Mines||Analysis Of The Initial Collapse Of The Overburden Over Long||The Influence Of Stream Valleys On Coal Mine Ground Control||Aerostatic Support System For Underground Coal Mines||A Simplified Two-Dimensional Analysis Of The Roof-Pillar-Flo||Comparative Studies In The Mechanics Of Grouted Roof Bolts||Seismic Studies Over Active Longwall Mines||Surface Ground Movements Over Longwall Mining In The Pittsbu||Effect Of Longwall Mining Subsidence On The Stability Of Sur||Study Of Quantitative Impacts To Ground Water Associated Wit||The Broken Rock Zone Around Tunnels And Its Support Theory||Subsidence In Indian Coalfields||Case Studies Of Depillaring Under Special Strata And Mining||The Control Of Surface Subsidence By Width/Depth Ratio And C||Design Of The Ventilation Shaft In The South Link Railway Tu|