Study of the fracture instability and fault slip risk of overlying strata during mining near faults

Mining activity near faults is the main reason for the frequent occurrence of rock burst accidents near faults. Based on on-site observation and monitoring, it is found that when the working face parallel to the fault strike is being mined, the overlying strata are more active. The degree of fault activation is intense. To deeply study the mechanism of induced rock bursts during the mining of underground coal seams, the Coulomb stress increment of the fault plane was introduced in a criterion for fault activation, and a mechanical model considering the fault slip induced by principal stress unloading was established. The results show that the risk of fault slip is related to the percentage of stress unloading (unloading amount) of the lateral principal stress and the axial principal stress and is especially sensitive to the unloading amount of the lateral principal stress. The excavation process of the working face was restored through numerical simulation, and it was found that the fault slip is closely related to the unloading stress in the horizontal and vertical directions, which verifies the accuracy of the theoretical model. The stress evolution of the overlying rock mass, the characteristics of fault slip, and their relationship during the mining of parallel faults are studied. The mechanical model is used to describe the fault sliding mechanism from the perspective of excavation unloading, and the research results provide theoretical support for fault rockburst prevention.