高地应力环境下引水隧洞软弱围岩稳定性分析

Stability analysis on soft and weak surrounding rock of diversion tunnel in high geostress zone

以实际深埋软岩引水隧洞施工为背景,在对导致大变形的围岩压力性质认识和力学行为分析的基础上,结合室内实验、数值模拟手段、施工变形监测数据和围岩—衬砌接触压力现场试验,研究了隧洞开挖后洞周位移分布特征、围岩变形和支护受力随时间发展规律。研究结论表明:(1)大主应力方向为垂直方向的高地应力环境中,隧洞软岩大变形以挤压型变形为主;(2)开挖面和二衬对约束隧洞空间位移分布具有重要作用;(3)软弱围岩变形发展和支护受力具有明显的流变特性和时间效应,及时施加二衬能有效限制流变变形的发展。在研究基础上提出了一些施工中有益于控制围岩稳定性的建议。

Taking the construction of deeply buried diversion tunnel as the study background, the distribution characteristics of the peripheral displacement, surrounding rock deformation and time-dependant development law of supporting stress are studied in combination with the relevant lab-experiment, numerical simulation, measured data of monitoring on construction deformation and in situ test on surrounding rock-lining contact pressure based on the understanding of the property of surrounding rock pres- sure that causes large deformation and the analysis on the mechanical behavior concerned. The study result shows that（ 1 ）within the environment of the high geo-stress with the major principal stress in a vertical direction, the larger deformation of soft rock is mainly the extrusion deformation; （2） the excavating face and the secondary lining play important roles on constraining the spatial displacement distribution of tunnel; （3） the development of soft surrounding rock deformation and the supporting stress have ob- vious rheological behaviors and time effects, and then placing the secondary lining can effectively restrict the development of the rheological deformation. On the basis of this study, some suggestions favorable to control the surrounding rock stability during construction are finally proposed as well.