浅埋偏压隧道洞口段软弱围岩失稳突变理论分析

含有断层的浅埋偏压隧道的断层错动引起围岩失稳是一个由渐变到突变的过程，具有非连续跳跃的特征，可以采用突变理论分析围岩破坏方式。以沪-昆客运专线长-昆湖南段CKTJ-Ⅸ标段某隧道洞口穿越断层破碎带为工程背景，根据围岩失稳情况，建立隧道穿越断层段的力学模型，构建断层围岩系统的总势能函数，求出突变模型的标准型式和分叉集方程；将拱顶下沉变形随时间变化的函数展开为泰勒级数，建立隧道围岩稳定状态判别式，实现突变模型和监测数据的融合。研究结果表明，围岩拱顶沉降变形随时间变化的函数与围岩失稳突变模型之间存在良好的转化关系；根据围岩失稳突变判据得出的围岩失稳状态与实际围岩破坏情况基本吻合，且判别式的组成型式简单，对于判断含有断层的浅埋偏压隧道围岩稳定性具有较强的实用性；判别式的大小与围岩的破坏程度之间存在一定的关联。

Instability analysis of soft surrounding rock in shallow tunnel portal under unsymmetrical pressure by catastrophe theory

For shallow tunnel under unsymmetrical pressure with fault, the surrounding rock failure caused by fault diastrophism is a process from anamorphic to mutational with characteristics of discontinuous changes and sharp jump values. Therefore, the surrounding rock failure modes can be analyzed by catastrophe theory. Taking the tunnel portal across fault facture zone of Shanghai-Kunming passenger dedicated line Changsha-Kunming Hunan CKTJ-IX section as the engineering background and according to the surrounding rock instability, the mechanical model for tunnel across the fault is established; the total potential energy function of fault surrounding rock system is built; and the standard type of catastrophe model and the bifurcation set equation are obtained. The time-dependent function of vault settlement deformation is transformed into Taylor series to build the criterion of tunnel surrounding rock stable state for the fusion of catastrophe model and monitoring data. The research results show that the time-dependent function of vault settlement deformation can be converted into the catastrophe model of surrounding rock instability. The surrounding rock instability based on the catastrophe criterion is identical to the actual damage of surrounding rock. The composition of criterion is simple. It has strong practicability for judging the stability of shallow tunnel under unsymmetrical pressure with fault. There is a certain correlation between the value of the criterion and surrounding rock damage degree.