弹性模量依赖围压的圆形洞室围岩破坏行为数值模拟

Numerical Simulation of the Failure Behavior of the Circular Tunnel Surrounding Rock Considering the Elastic Modulus Dependent on the Confining Pressure

在考虑拉伸截断及非线性屈服准则的自定义本构模型中,又考虑了弹性模量(弹模)受围压的影响,模拟了两种网格、不同本构模型及加载方式条件下的洞室围岩的破坏行为。在第1种网格中,洞室围岩被剖分为辐射网格,采用"先挖洞,后加载"的方式及理想弹-塑性本构模型进行计算;在第2种网格中,洞室围岩被剖分为矩形网格,采用"先加载,后挖洞"的方式及弹-脆-塑性本构模型进行计算。计算结果表明,对于第1种网格,随着弹模的围压影响系数的增加,洞室围岩的应变、位移及塑性区半径均有所减小,被监测单元的环向应力的峰值有所降低,不同本构模型的计算结果的差别逐渐显现。对于第2种网格,当弹模的围压影响系数较低时,围岩中形成了4个对称的V形坑,随着弹模的围压影响系数的增加,V形坑的个数及尺寸明显减少,这可由洞室围岩的应力、位移及剪切应变增量均有所减小得到解释。

In the user-defined constitutive model considering tension cut-off, nonlinear yield criterion and influence of confining pressure on elastic modulus, the failure behavior of the circular tunnel surrounding rock was modeled using two shapes＇ grids with different constitutive models and loading conditions. In the first kind of grid （radial grid）, an ideal elastoplastic constitutive model was used and a circular tunnel is excavated before the model is loaded to an equilibrium state in numerical simulation. In the second kind of grid （rectangular grid）, an elastic-brittle- plastic constitutive model was used and a circular tunnel is excavated after the model is loaded to an equilibrium state in numerical simulation. The results show that in the first kind of grid, the strain, displacement, plastic zone and the peak value of hoop stress of monitored elements are lowered as the elastic modulus is influenced increasingly by the confining pressure, and the differences of results based on the different constitute models appear gradually; in the second kind of grid, four symmetric V-shaped notches are found as the elastic modulus is influenced slightly by the confining pressure. The number and the size of V shaped notches decrease significantly as the elastic modulus is influenced increasingly by the confining pressure. This phenomenon can be explained by the results in the first kind of grid.