中文摘要：

为探究深埋软岩隧道在开挖无支护阻力条件下的围岩安全性受剪胀软化效应的影响机制,基于修正Mohr-Coulumb强度准则（简称修正M-C准则）和增量型本构关系（即Levy-Mises本构关系）,通过对轴对称隧道进行弹塑性求解,研究岩石剪胀效应对软岩隧道安全性的影响。依据算例,分析软化模量、内摩擦角和黏聚力等参数对隧道的安全解（如隧道塑性软化区和塑性残余区边界线以及原岩应力阈值）的影响。计算中对支护反力进行恰当处理,并考虑软岩隧道的特殊力学性质（即剪胀效应）,所得结果不仅是对现有理论解的补充和完善,而且更加符合工程实际。

英文摘要：

In order to analyze influence of dilatancy softening effect on safetyof surrounding rock in deep soft rock tunnel excavation under the condition of no support resistance, elastic-plastic solutions of an axisymmetric tunnel were obtained, based on the amendment Mohr-Coulumb strength criterion（hereinafter referred to as the rule of amendment M-C） and the incremental constitutive relationship（namely Levy-Mises constitutive relation）.By means of a case analysis,effects of softening modulus, internal friction angle and cohesive force on the tunnel plastic solution（such as tunnel surroundingplastic softening zone and the plastic residual area boundary, and the original rock stress threshold） were analyzed. Owing to treating properly handle support reaction force and considering the special mechanical properties of soft rock tunnel（that is, the dilatancy angle and softening modulus）, this paper can obtaine a result which is to supplement and perfect the existing theoretical solution, and is in line with the engineering practice to a greater ectent.