考虑塑性区强度参数劣化的圆形巷道冲击地压临界条件研究

针对大量冲击地压事故发生于巷道的实际情况，综合考虑开挖面空间效应、中间主应力效应、塑性区剪胀特性、塑性区强度和变形参数的变化5个影响因素，得到了巷道围岩应力与位移分布规律，基于统一强度理论和塑性软化本构模型，应用扰动响应判别准则，建立圆形断面巷道冲击地压发生的临界条件，结合试验模拟验证分析，结果表明:巷道冲击地压的临界条件与围岩支护方式、初始强度参数及塑性区强度参数的变化密切相关；临界塑性半径、临界载荷均随支护力的增大而单调增加；在开挖面附近，虚拟支护力较大，巷道围岩以发生弹性变形为主，发生冲击地压概率较低，只有在距开挖面一定距离位置处，虚拟支护力逐渐降低，巷道围岩出现塑性区，且塑性区达到一定值时，冲击地压才具有发生的可能性；临界塑性半径随初始黏聚力增大而降低，临界载荷随初始黏聚力增大而增加；当塑性区黏聚力劣化较快时，容易发生冲击地压。

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 tunnel,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 displacement 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 virtual 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.