扩容角对圆形巷道岩爆过程的影响

Numerical simulation of the rockburst processes of a circular tunnel at different dilation angles

利用FLAC模拟了不同扩容角时圆形巷道的岩爆过程。为了模拟巷道开挖,利用编写的FISH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。文章的模拟分为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FISH函数,开挖巷道;最后,计算重新开始,直到达到静力平衡状态。模拟结果表明,随着扩容角的增加,剪切带变宽,岩爆坑变深,破坏单元数目增多,破坏区变大。当扩容角较低时,高剪切应变集中于"狗耳"形岩爆坑位置,剪切带与巷道周边切线之间的夹角较大;当扩容角较高时,高剪切应变集中于巷道周边的一些位置上,剪切带与巷道周边切线之间的夹角较小。该研究结果与Roscoe,Arthur理论相符。

Rockburst processes of a circular tunnel are modeled by use of FLAC at different dilation angles.To model the tunnel excavation,a FISH function is written and used to delete the elements in the tunnel.For rock elements exhibiting linear strain-softening behavior beyond the occurrence of failure and then ideal plastic behavior,the failure criterion is a composite Mohr-Coulomb criterion with tension cut-off.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,a tunnel is excavated using the written FISH function.Thirdly,the calculation renews to achieve a new equilibrium state.Results show that with an increase of the dilation angle,the shear band becomes wider;the dog-ear or V-shaped rockburst notch becomes deeper;the number of failed elements is greater and the plastic zone becomes bigger.At lower dilation angles,the apparent strain localization phenomenon is localized at V-shaped notches,the angle between a shear band and the tangential line of the tunnel surface is higher.However,at higher dilation angles,the angle is lower and the apparent strain localization phenomenon is localized at the tunnel surface.The present numerical results about the shear band inclination are consistent with the Roscoe and Arthur theories.