On the fracture characteristics of overlying key strata related to the seismicity under deep coal mining
In the process of mining deep coal resources,the occurrence of strong mine earthquakes has become an important reason restricting the safe and efficient production of deep coal mines.The sudden release of strain energy caused by the instant breaking of key strata in deep coal mining is one of the important causes of the mining-induced seismicity.Aiming at the 63upper06 working face of the Dongtan coal mine,the PFC2D numerical software is used to simulate the failure process of overlying key strata in the process of coal mining.The evolution of the mining stress field is also investigated.Utilizing the single generalized displacement thick beam mechanics theory,the mechanical process of multiple key strata is inferred.The results indicate that the overlaying key strata failure types could be classified as suspended failure and overhanging failure.The vertical stress in overlying strata steadily decreases while the horizontal stress rises during mining as a result of the force arching effect of the changing mining stress field.The maximum tensile stress formula,maximum suspension distance,suspension distance of key strata before suspension,and mechanical mechanism of key strata covering deep coal mining are all derived.The research results are of great significance for the advancement of the theory of coal overburden migration in deep mining.
rock mechanicsdeep coal minebreaking of key layersPFC2Dchange of mining stress fieldmechanical mechanism
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