ABSTRACT:

Rib falls are serious safety hazards in underground coal mines. Studies of injuries and fatalities caused by rib falls have shown that the significant mining conditions that contribute to rib falls are mining height, depth of cover, and stress resulting from mining of multiple seams. In longwall mining, rib stability in gate entries is also influenced by the induced abutment pressures. To reduce the risk of rib injuries and fatalities in longwall mining, it is important to understand the mechanisms of rib failure under different geologic and mining conditions, and the requirements for rib support in the gate entries. Rib scoping was performed by NIOSH researchers to detect fractures in the ribs of the gate entries in the Pittsburgh coal seam. Rib fractures and failures were observed for various loading conditions throughout different mining cycles. Numerical modeling was performed to calibrate a coal mass model to the field data and to further predict rib fractures under different abutment stress levels. Based on field monitoring and numerical modeling, a conceptual model is proposed for considerations of rib support in longwall gate entries.

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