Mechanism of rock burst induced by mine earthquake and the time-space characteristics of in steep and extremely thick coal seam

Aiming at the problems of complex occurrence environment, frequent mine earthquakes and high impact risk in steep and extremely thick coal seams, through the construction of rock pillar mechanical model and numerical model, the statistical analysis of on-site mine-induced earthquake events, the law of coal-rock catastrophe in steep and extremely thick coal seam mining is obtained, and the mechanism of mine-induced shock in steep and extremely thick coal seam based on dynamic and static load theory is formed. Five microseismic indicators are selected to deeply analyze the abnormal precursors and time span characteristics of mine earthquakes, to show the impact danger and grasp the opportunity of reinforcement and pressure relief. Through the location of microseismic events, the spatial characteristics of mine earthquakes are got, and the key areas of pressure relief are clearly defined. Based on the temporal and spatial characteristics of mine earthquakes, the anti-scour strategy is put forward. The results show that the bending deformation effect of rock pillar in steep and extremely thick coal seam becomes more and more obvious with the increase of mining depth, and the energy accumulation in rock pillar increases with the increase of mining depth. Rock pillar and high-energy accumulation area in coal seam are broken on a large scale by mining disturbance, resulting in dynamic load vibration wave, and the superposition of dynamic and static loads is easy to induce impact. The total energy-frequency, A(b) value and S value all appear low-value anomalies, while B value and P(b) value all appear high-value anomalies, and the abnormal span indicates the process of mine earthquake preparation. The total energy-frequency, A(b) value and S value all jump to high values, while B value and P(b) value all drop to low values. Before the mine earthquake, there is an obvious lack of earthquake in a certain area in space. The higher the degree of lack of earthquake, the greater the energy of mine earthquake. According to this, reinforcement and pressure relief measures can be taken to reduce the impact risk from the source. Anti-scour strategies include fully relieving the pressure of rock pillars and coal seams, weakening the source and path of impact, and strengthening the support of stope and roadway to make them have certain anti-scour ability. However, there is no guarantee that there will be no impact danger during mining. It is necessary to closely monitor the coal and rock activities in the mining process and identify the spatio-temporal abnormal precursors of high-energy mine earthquakes, so as to take some timely and accurate safety protection measures such as reinforcement and pressure relief, support and evacuation.