Critical condition of rock burst in the circular tunnel based on the strength parameters of the degradation in the plastic zone

In terms of the critical condition of rock burst in the circular tunnel based on the strength parameters of the degradation in the plastic zone,in view of the fact that most of the occurrence of rock burst event is located in the tun- nel,considering the spatial effect of excavation face,the intermediate principal stress effect,the plastic zone’ s shear expansion characteristics,the plastic zone strength and deformation parameters,the distribution law of stress and dis- placement of surrounding rock is obtained. Based on the unified strength theory and the plastic softening constitutive model,the critical condition for the occurrence of rock burst in the circular section is established by using the criterion of disturbance response. The results show that the critical condition of rock burst is closely related to the support mode,the initial strength parameter and the strength parameters of the plastic zone. The critical plastic radius and the critical load increase monotonically with the increase of the support force. In the vicinity of the excavation face,the vir- tual support force is large,thus elastic deformation occurs only in the surrounding rock of the roadway,and the probability of occurrence of rock burst is low. Only in the far away from the excavation face,the virtual supporting force is gradually reduced,and the plastic zone of surrounding rock appears,and the possibility of the occurrence of rock burst occurs when the plastic zone is large enough. The critical plastic radius decreases with the increase of initial cohesion, and the critical load increases with the increase of initial cohesion. Rock burst occurs easily when the cohesive in the plastic zone is deteriorated rapidly.