Failure and instability mechanism of anchored surrounding rock for deep chamber group with super-large section under dynamic disturbances

Abstract

The interaction of super-large section chamber group in deep and close-distance condition will lead to stress concentration and wide failure range of surrounding rock, especially under dynamic disturbances. In this paper, numerical simulation software FLAC3D is used to establish the calculation model based on the field condition of coal gangue separation system in Longgu Coal Mine. The deformation and failure evolution of chamber group under different chamber spacing and dynamic loads are studied by using built-in dynamic module. The simulation results show that: With the decrease of chamber spacing, the deformation and failure degree of surrounding rock gradually increases, and the overall failure and instability occur eventually. Compared with the static load, the range of critical spacing under dynamic disturbance is enlarged by 33.3%-50%. Meanwhile, the response of anchored surrounding rock is gradually intensified with the dynamic load strength increase, and the critical strength of failure and instability is about 4.0-4.5 MPa. Based on the elastic-plastic mechanics and elastic wave theories, the mechanical model of anchored surrounding rock under dynamic and static loads is established. The failure and instability criterion are obtained. The anchored surrounding rock can be divided into three states: overall stability, static failure and dynamic failure. On this basis, the analytical expression of critical distance between failure and instability is presented. Finally, in-site calculation and field monitoring verify the rationality and feasibility of the theoretical analysis. This study provides a reference for layout design and stability control of super-large section chamber group.

Keywords

• dynamic disturbance
• super-large section
• chamber group
• deformation and failure
• instability