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|The U.S. Bureau of Mines is investigating the use of in-seam seismic methods to monitor stress-induced changes in coal near the working face of longwall mines. Seismic surveys performed through a longwall panel and pillars near the face can provide valuable information on geologic anomalies, high stress regions, tailgate support performance and other conditions that could endanger miners or interrupt production. This paper describes the details of the equipment and data analysis techniques used, and the significant results obtained and their implications for ground control. Using seismic tomography, it is possible to conduct measurements on the pillar and reconstruct an image representing the internal velocity distribution. Successive measurements over several days identify changes in velocity attributable to changes in stress. Several field measurements were conducted at a western U.S. longwall mine to observe stress induced changes within the panel and pillars during mining. A permissible data acquisition system was designed to meet mine safety requirements for operation in gassy air. Certification from the Mine Safety and Health Administration (MSHA) was obtained, and this approved system was used to monitor stress changes in several pillars as the longwall face passed during first panel mining. Tomographic surveys were completed across the longwall panel to map the apparent abutment stresses ahead of mining. Velocity distributions show an increase in vertical stress across the panel from the headgate to the tailgate. Additionally. a yield zone along the face near the tailgate and the forward abutment approximately 100 feet outby the face in the tailgate side of the panel were detected. These results agree well with data obtained from other instrumentation emplaced in the panel near the tailgate. Using velocities for both compressional and shear waves, the Poisson's ratio was calculated for the panel.|
Additional chapters/articles from the SME-ICGCM book Proceedings of 13th International Conference on Ground Control in Mining
|Cable Bolting - Potential Applications For Variable Strata C||Evaluation Of Support Performance In A Highly Stressed Mine||Operational Experience With FLEXIBOLT Systems In Australian||Roofbolting In The Cape Breton Development Corporation'||Some Factors Influencing Stability Of Longwall Gateroad||Design Of Roadway Support Using A Strain Softening Model||Automation Of A Progressive Failure Procedure For Analysis O||The Massive Collapse Of Coal Pillars - Case Histories From T||Time Dependent Strength Of Coal Strata For Long-Term Pillar||Yield Pillar Behavior At Jim Walter No. 7 Mine Stress And St||A Comparison Of Overburden Response Due To Longwall Mining||Longwall Ground Behavior Characteristics In The Illinois Coa||Cavability Study Of A Competent Roof - A Case Study||Roof Pressure Monitoring Using The Integrated Longwalt Autom||Longwall Production, Maintenance, And Roof Control System||The Design And Selection Of Powered Supports For Application||Tailgate Support Practice In U.S. Longwall Mines - A Survey||Influence Of Support Capacity And Geometry On Tailgate Suppo||Innovative Concept In Tailgate Entry Support: Elimination Of||Resin-Grouted Cables For Longwall Tailgate Support Stability||Tailgate Roadway Convergence: A Key Indicator Of Potential G||Assessment Of Wood And Alternative Materials For Supplementa||Experience With The Boundary Element Method Of Numerical Mod||The Fault At The End Of The Tunnel||Microseismic Monitoring In The Sydney Coalfield||Realistic Design Of Ground Control Based On Geotechnical Dat||Underground High Resolution Seismic Method As A Low Cost Alt||Pillarless Longwall Mining For Multiple Seams||Stable Entry Design In A Multi-Seam Environment||Evaluating Roof Control In Underground Coal Mines With The C||Hazard Mapping Combining Geostatistical Modeling Of Coal Min||Stereological Sampling And Analysis For Characterizing Disco||Determining Horizontal Stress Direction Using The Stress Map||Stability And Stress Evaluation In Mines Using In-Seam Seism||Hydrogeologic Effects Of Subsidence At A Longwall Mine In Th||Monitoring Railroad Response To Mining Subsidence And Assess||Study On The High-Pressure Grouting Of The Overburden For Su|