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|An investigation was conducted to determine the nature and frequency of coal mine roof failure beneath valleys. A mechanism for this failure, and suggestions for controlling this problem are presented. Hazardous roof conditions identified in a number of mines were positively correlated with mining activities beneath stream valleys. Mine maps with overlays of unstable roof and locations of stream valleys show that 52% of the instances of all unstable roof in the surveyed mines occurred directly beneath the bottom-most part of the valley. The survey also showed that broad, flat-bottomed valleys were more likely to be sites of hazardous roof than narrow-bottomed valleys. Evidence of valley stress relief was found beneath a number of valleys in the form of bedding-plane faults and low-angle thrust faults. This type of failure, previously believed to be only a shallow phenomenon, was found at mining depths as great as 300 ft. In situ horizontal stress measurements in a mine beneath a valley and the adjacent hillsides confirmed valley stress re1ief. Underground mapping showed that roof falls in excess of 100 ft in length and up to 25 ft high closely aligned with the valley axis. Numerical analysis of 13 valleys overlying one mine property showed the effect of the valley excavation on horizontal and vertical stress. Thickness of cover, valley shape, and the orientation of the valley relative to the maximum regional horizontal stress all influence the "valley effect" on roof stability.|
Additional chapters/articles from the SME-ICGCM book Tenth International Conference on Ground Control in Mining Proceedings (ICGCM) 10th
|Practical Aspects Of Longwall Pillar Design||Assessment Of Underground Structural Design||Load And Convergence Measurements In Longwall Faces And Desi||A Model Of Shield-Strata Interaction And Its Implications Fo||Stability Of Interpanel-Pillar And Deformation Of Gateroad D||Use Of Polymer Grids For Longwall Shield Recovery||Methods Of Controlling Thick And Strong Roof In Longwall Min||Tensioned Point Anchor Resin System Versus Non-Tensioned Ful||Thrust Bolting: A New Innovation In Coal Mine Roof Support||An Alternative To A Manual Torque Check On Roof Bolts||Shear Bond Stresses Along Cable Bolts||An Underground Trial Of Cable Slings For Remedial Support Of||Mobile Roof Support For Retreat Mining||Application Of Time Domain Reflectometry To Ground Control||An Examination Of Energy Calculations Applied To Coal Bump P||Delineation Of Abandoned Workings With An In-Seam Seismic Me||Remote Detection Of Abandoned Mine Workings Using Radio Imag||Effects Of Surface Topography On The Stability Of Coal Mine||Site Characterization For Ultra-Close Multi-Seam Mining||Mining Under Rivers In Fuxin Coal Mines||Use Of Database In Ground Control To Identify Weightings And||Integrating Ground Control And Mine Site Data Through A Geog||Determination Of The Rock Strength From Portable Rock Tester||Mine-Wide Physical Property Trend Identification Using Porta||Subsidence Prediction In Illinois Coal Basin||Determination Of The Stopline Subsidence Profile Of Phalen 2||Evaluation Of Subsidence Parameters For Inclined Seams In UK||Measurement Of Structural Deformation And Tilt During Subsid||Drag Picks - Influence Of Tool Geometry And Angle Of Arrack||Roof Sounding Device - A Loose Rock Detector||Advanced Surveying Method For Measuring Roof Convergence||Geomechanical Substantiation Of Extraction Of Undermined Ore||Relationship Between Floor Rock Stress And Floor Failure||The Influence Of Geomining Parameters Over Stress Distributi||Finite Element Modeling Of Subsidence Induced By Underground||The Structural Response Of A Steel Lattice Transmission Towe|