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Geologic Factors in Coal Mine Roof Stability--a Progress Report.
MISSING :27 pages
This report summarizes 10 selected Bureau of Mines research contract reports produced from 1970 to 1980 that consist largely of geologic studies of coal mine roof support problems. Significant highlights from the contract final reports are discussed and presented in practical terms. The selected reports focus on the Appalachian and Illinois Coal Mining Regions. In the Appalachian Coal Region, two geologic structures, roof rolls and slickensides, predominate over all structures as features that directly contribute to roof falls. Studies of these and other structures are reviewed, and improved methods of utilizing drill core and core logs to prepare hazard maps are presented. Among the reports described are several on the weakening effects of moisture on shale roof, as determined from both laboratory and underground measurements, and an assessment of air tempering as a humidity-control method. Also summarized are findings concerning the time lapse between roof exposure and permanent support installation as a factor in the effectiveness of roof bolting.
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