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|Unusual circumstances may require that a longwall retreat into or through a previously driven room. The operation can be completed successfully, but there have been a number of spectacular failures which exposed miners to serious roof fall hazards. To help determine what factors contribute to such failures, the National Institute for Occupational Safety and Health (NIOSH) compiled a comprehensive international database of 130 case histories. The cases include five failures where major rock falls occurred in front of the shields, and six even more serious failures involving major overburden weighting. This suggests two room failure mechanisms. The first is a roof fall type failure caused by loading of the immediate roof at the face as the fender narrows. The second is a weighting type failure caused by the inability of the roof to bridge the recovery room and face area, and affecting rock well above the immediate roof. The data indicate that the roof fall type of failure is less likely when intensive roof reinforcement (bolts, cables, and trusses) is employed together with higher-capacity shields. The overburden weighting failures, in contrast, occurred when the roof was weak and little standing support was used.|
Additional chapters/articles from the SME-ICGCM book 17th International Conference on Ground Control in Mining (ICGCM)
|Gateroad Pillar Extraction Experience at Jim Walter Resource||Stability of Backfilled Cross-panel Entries During Longwall||Mining Through In-panel Entries and Full-face Recovery Room||Cutable and Variable Yield Cement Cribbing Successfully Supp||International Experience with Longwall Mining into Pre-drive||Analysis of Geologic and Geotechnical Conditions and Their E||Comparison of Ground Conditions and Ground Control Practices||Application of Microseismic Monitoring to Longwall Geomechan||Control of Hard-to-Collapse Massive Roofs in Longwall Faces||A Study of Periodic Weighting of Longwall Supports||Effects of Panel Mining Sequence and Retreat Direction on th||Controlling Roof Beam Failures From High Horizontal Stresses||Roof Control Under Conditions of Shallow Depth and High Hori||Assessment of Roadway and Yielding-pillar Performance During||Practical Stress Modeling for Mine Planning||The Design of Room and Pillar Mining Systems in the UK||Geotechnical Planning and Development of the BHP Minerals Sa||Coal Pillar Life Prediction in the Vaal Basin, South Africa||An Analytical Approach to Determine Stress Distribution in L||In Situ Strength Testing of Rocks with the Borehole Penetrom||Performance and Safety Considerations of Hydraulic Support S||A Decade of Mobile Roof Support Application in the United St||A Critical Study of Strata Behaviour During Extraction of Pi||Progression of Longwall Gateroad Support as Conditions Chang||Application of the Coal Mine Roof Rating, Derived from Drill||The Effects of Reduced Annulus in Roof Bolting Performance||Laboratory and In Situ Results of a Slip Nut Yielding Rock B||Field Monitoring of Rock Bolting Performance in Weak Roof St||A Case Study of Bolt Performance in a Two-entry Gateroad||Automated Temporary Roof Support Systems: An Update||Safety and Productivity Innovations in Mechanized Bolting||Factors Influencing Intersection Stability in U.S. Coal Mine||Analysis of the Effect of Rate of Extraction on Strain Devel||Analysis of Panel Stability for Post-Mining Slurry Injection||Development of Timedependent Surface Subsidence Over the Tot||Transversely Elasto-Plastic Analysis of Surface Subsidence A||Landslide Occurrence and Causation in Steep Slope Areas of A||Rock Bursting and Seismicity During Ramp Development, Lucky||Advances in Remote Sensing Techniques for Monitoring Rock Fa|