Mechanism of rock bursts in a large inclined extra-thick coal seam under the condition of upper slice mining: a case study

With the increase of mining depth and mining intensity of the large inclined extra-thick coal seam (LIETCS), the number of rock bursts increases significantly. In this paper, based on a rock burst during upper roadway driving of the LIETCS, the distribution characteristics and fracture mechanism of microseismic (MS) events are analyzed using data statistics and seismic moment tensor inversion. By means of mechanical analysis and numerical simulation, this paper studies the static load distribution characteristics and dynamic load action effect of the LIETCS under upper slice mining condition. Based on the theory of dynamic and static combined load, the mechanism of rock bursts is proposed. The results show that the coal and rock mass of the LIETCS are mainly destroyed by shearing. The "shear-clamping" stress produced by the joint action of the roof and floor is the static load source. In upper slice mining, the shear stress and energy of the coal pillar behind the slice and the coal body below the coal pillar always remain high. Under the superposition of floor dynamic load, the regional stress environment changes, which induces rock bursts. This study provides a theoretical basis for rock burst prevention under similar conditions.