圆形巷道围岩的环向应力及发生岩爆单元分布的数值模拟

利用FLAC模拟了不同水平方向压力（小于竖直方向压力）及岩石峰后不同脆性条件下的圆形巷道破坏过程。岩石服从莫尔-库仑剪破坏与拉破坏复合的破坏准则,破坏之后呈现应变软化-理想塑性行为。监测了模型中第1象限对角线上的单元环向应力分布及演化规律。根据徐林生和王兰生提出的环向应力岩爆判据,判断模型中各单元是否发生岩爆。模拟结果表明：当竖直方向压力一定时,随着水平方向压力的增加,V形坑的顶点和巷道中心的连线与模型水平轴的夹角,由小于45°向接近45°发展;同时,巷道围岩中发生破坏的单元数及发生岩爆的单元数均增加,环向应力的峰值增大。随着岩石峰后脆性的增强,剪切带趋于明显,容易汇合形成V形坑;同时,巷道围岩中发生破坏的单元数及发生岩爆的单元数均增加,环向应力的峰值向围岩内部移动。

Numerical Simulation of the Distribution of Tangential Stresses and Elements Occurring Rockburst in the Surrounding Rock of a Circular Tunnel

Rockburst process of the surrounding rock of a circular tunnel is modeled by use of FLAC.Effects of the horizontal stress that is less than the vertical stress and the post-peak brittleness of rock are studied.The rock elements exhibit linear strain-softening behavior after the occurrence of failure and ideal plastic behavior and the failure meets the composite Mohr-Coulomb criterion with tension cut-off.The tangential stress of a row of elements in the surrounding rock is monitored.The tangential stress rock-burst criterion proposed by Xu and Wang is used to determine the state of elements.Numerical results show that the angle between the line（linking the V-shaped notch tip and the central point of the tunnel） and the horizontal axis of the tunnel increases to 45°from that less than 45°as the horizontal stress is increased. As the horizontal stress increases,the number of the failed elements and the elements occurring rockburst increases and the peak tangential stress is increased.At higher post-peak brittleness of rock,the shear bands become apparent,and it is easy to form the V-shaped notches.The number of the failed elements and the elements occurring rockburst increases.The distance between the rock with peak tangential stress and the tunnel surface is increased.