Study on the response mechanism characteristics of fault activation under the mining effect of thick coal seam

Aiming at the problem of fault activation instability induced by deep thick coal seam mining, taking 8404 working face of Madaotou Coal Mine in Datong Coalfield as the engineering background, the response mechanism of fault activation and crack evolution law under mining stress are revealed by using similar material simulation test and continuous-discrete coupling numerical simulation method. The results show that the risk of fault activation during thick coal seam mining significantly increases with a higher stress concentration coefficient, greater burial depth, and closer proximity of the working face to the fault. The smaller the fault dip angle, the higher the activation probability of the normal fault. Under mining conditions, the fault displacement exhibits progressive expansion, with a maximum displacement of 15.9 mm. The density of acoustic emission events increases in synchrony with the displacement rate. The fault activation process can be divided into three stages: distal response, local slip, and overall instability. The crack type in the fault zone changes from far-field tensile failure to near-field shear failure. The lower part of the fault is dominated by shear stress, and the amount of slip is significantly greater than that in the upper part. When the working face is located in the footwall of the fault, the lower part of the fault is most affected by mining. These research findings provide a theoretical basis for early disaster warning and prevention of fault activation during deep, thick coal seam mining.