不同强度岩石中开挖圆形巷道的局部化过程模拟

利用FLAC模拟了不同粘聚力条件下圆形巷道的局部化过程。为了模拟巷道开挖,利用编写的F ISH函数删除巷道内部的单元。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。文中模拟分为3步：首先,将静水压力施加在模型上,直到达到静力平衡状态;然后,利用编写的F ISH函数开挖巷道;最后,计算重新开始,直到达到静力平衡状态或者塑性流动状态。模拟结果表明,随着粘聚力的降低,巷道围岩的破坏模式首先由孔壁附近零星单元的破坏向4个对称的小V形坑式剪切破坏转变,然后由包含若干小V形坑的大V形坑式剪切破坏向巷道全断面的破坏转变。前三者破坏发生后,巷道围岩仍然能保持稳定。与最大塑性拉伸应变相比,最大剪切应变增量、最大塑性剪切应变要高得多;最大剪切应变增量、最大塑性剪切应变相差不大;随着粘聚力的增加,三者均越来越小。

Numerical Simulation of Strain Localization Processes of a Excavation Circular Tunnel with Different Rock Strengths

Strain localization processes of a tunnel at different cohesions are modeled using FLAC.To model the tunnel excavation,a FISH function is written and used to delete the elements in the tunnel.Rock elements exhibit linear strain-softening behavior beyond the occurrence of failure and then ideal plastic behavior.A composite Mohr-Coulomb criterion with tension cut-off is used.The present calculation is divided into three steps.Firstly,a hydrostatic pressure is applied to the plane strain model until a static equilibrium state is reached.Secondly,the tunnel is excavated using the written FISH function.Thirdly,the calculation renews to achieve a new equilibrium state or a plastic flow state.Results show that as cohesion decreases,the failure modes of the tunnel surrounding rock firstly changes from minor local failure in tunnel surface to shear failure in four smaller symmetric V-shaped rockburst notches and then from shear failure in bigger V-shaped rockburst notches comprising smaller notches to entire section collapse due to longer shear band intersection.For the former three failure modes,the surrounding rock can sustain its stability after rockbursts.Compared with the maximum tensile strain,the maximum shear strain increment and plastic shear strain are higher and the values of the maximum shear strain increment and plastic shear strain are closer.As cohesion increases,the three kinds of strains decrease.