Analysis Of The Stability Of Surrounding Rocks Of Tunnels Considering Pore Pressure

With the accelerating pace of urban modernization, the congestion of urban traffic is attracting more attention. In recent years, a large number of subway projects in China began to put into construction, so the stability of tunnels and surrounding rock construction has become the highest priority. Underground water threats the stability of the tunnels and many accidents induced by underground water have been reported.In the process of verifying the stability of the tunnels using the analytical or numerical simulation methods, the accuracy of the selected mechanical parameters directly determine the scientific nature of the conclusion. In this thesis, the stability of surrounding rocks of subway tunnels under the influence of pore pressure analyzed. Besides, the mechanical and seepage parameters are obtained through using back analysis method optimized and genetic algorithm. The mechanical parameters are also adopted for the analysis of the deformation caused by tunnel excavation. The research presented in this thesis can be summarized as follows:(1) The theory and finite element method of seepage in fractured rock mass are introduced in detail. Besides, in order to analyze the failure mechanism of surrounding rocks in shallow buried tunnels, the three-dimensional numerical model of a single-hole tunnel considering pore pressure is established to simulate the development of plastic zone in the seepage-stress coupling state and the influence of different groundwater level on tunnel stability is analyzed.(2) The influence of several factors on the stability of parallel tunnels is considered, such as different depths, spacings and construction methods. Based on the gray relational theory, the contributions of the mechanical and seepage parameters to the displacement of the tunnels are studied through MATLAB programming, and a series of important conclusions are drawn.(3) An improved method combined by genetic algorithm and displacement back analysis is proposed to calculate the mechanical parameters of surrounding rocks, and the feasibility of the improved method in estimating the mechanical parameters is verified. The project of Qingdao subway tunnel is used as the engineering background. The mechanical parameters of the surrounding rocks of Qingdao subway tunnel are retrieved through MATLAB calling ABAQUS, and the accuracy of the calculated parameters is verified based on the engineering monitoring data.(4) The mechanical parameters obtained using the proposed method are adopted for the analysis of the stability of Qingdao subway tunnels,which also provide a scientific basis for the selection of supporting methods. These conclusions provide the basic recommendations for the safety of the subway tunnels construction.