Evolution law and risk analysis of fault-slip burst in coal mine based on microseismic monitoring

Abstract

Fault activation is a primary cause of rockburst in working faces of coalmines. To reveal the full-cycle impact gestation process, a numerical model consisting of a normal fault is established using FLAC^3D. The spatio-temporal evolution laws of the displacement field, stress field, strain field, and energy field of coal seam during the advance from hanging wall to footwall are obtained. Additionally, the energy level frequency division characteristics and the spatio-temporal distribution of the energy levels of microseismic signals during the working face crossing the fault are analyzed. The relationship between the risk level of fault-slip burst and microseismic information, stress field, strain field, and energy field around the fault region are established. This lays a foundation for implementing fault-slip burst risk classification control in deep working faces mining through faults. The results show that the distance between the working face and the fault significantly influences the energy concentration of the coal pillar, the rocks in footwall exhibiting a higher energy concentration than that in hanging wall. The spatial position relationship between the working face and the fault affects the failure mode of the coal and rock mass. The stress field, strain field, and displacement field of the coal seam and its roof or floor in the fault region show significant differences in sensitivity to the distance between the working face and the fault. Microseismic events indicate that fault activation can be divided into three stages: stress development, energy storage, and structural activation. During stress development and structural activation, there are more microseismic events and higher energy values. The microseismic energy of the working face is primarily concentrated within 10–20 m from hanging wall and throughout footwall of the fault. In addition, the pre-evaluation results of the impact risk of the working face prove that the evaluation model can effectively distinguish the leading role of different working face distances from fault. This provides reference and guidance for risk assessment of fault-slip bursts in deep working face mining through faults.