ABSTRACT: There is controversy as to the cause of catastrophic failures occurring when mining coal under strong roof. The U.S. Bureau of Mines presents a hypothesis that catastrophic mine roof failure is due to the formation of a macrocrack (dilatant zone) in the rock mass above a pillar or longwall panel immediately before roof collapse. The macrocrack closes upon itself during roof caving. From appropriate energy calculations, sufficient energy is available from this model to produce tremors whose energy release is equivalent to local earthquake magnitudes between ML = 2.0 ? 3.5. This energy release is applied to a model of damage criterion for propagation of high-amplitude compressive stress waves through the mine workings. Using a particle velocity damage criterion of 0.30 m/s as needed to induce tensile cracking at free surfaces in coal, the area of damage from a ML = 3.6 mine tremor (NEIS) in a Utah coal mine is calculated to be about 105 m2, corresponding closely to the area (7.6 x 104 m2) of observed damage.

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