地应力对洞室轴线布置影响的二维数值分析

2-D Numerical Analysis on Influence of In-situ Stress on Tunnel Axis Orientation

深埋洞室处于高地应力条件下,水平应力常大于垂直应力,且水平方向应力也不均匀,洞室稳定性主要受初始应力场控制。采用可以施加轴向应力的二维非线性有限元方法,计算模拟并列双洞和单洞,研究自重应力场、最大主应力与洞线平行和垂直等三种应力场条件、两类岩石地下洞室轴线的选择对围岩变形及稳定的影响。结果显示,最大主应力与洞轴平行时,塑性区主要分布在边墙部位;最大主应力与洞轴垂直时,塑性区主要分布在洞室顶底部。《水工隧洞设计规范》中洞线宜与最大主应力方向一致的适用性是有条件的。

Deeply buried tunnels usually lie in high stress fields, in which horizontal stresses are not uniform and far larger than vertical stresses, and tunnel stability is dominated by the original in-situ stresses. With three-dimensional nonlinear finite element method, the effects of tunnel in axis orientation on the displacement and stability of two types of surrounding rocks are studied systematically for two parallel tunnels and single tunnel. The tunnel lies in different kinds of rocks and in such different original stress fields that the maximum horizontal principal stress is parallel to or perpendicular to the axis or the stress field is gravity. The numerical analysis results show that the plastic zones occur in the side wall of the tunnel mostly when the horizontal maximum principal stress is parallel to the tunnel axis, while the plastic zones distribute in the top and bottom of the tunnel when the horizontal maximum principal stress is perpendicular to the tunnel axis. It is concluded that the instruction of tunnel axis should be parallel to horizontal maximum principal stress regulated by the ＂specification for design of hydraulic tunnel＂ is not available for the stability of tunnel always.