The Interaction Analysis Of Composite Support And Surrounding Rock Of Deep Tunnel

Engineering problems like large deformations, high stress rock burst and crown collapse are often met during the excavation and support of deep tunnels. The supporting structure usually need to bear high support resistance under the condition of high ground stress. So, it is important to make further research in the interaction analysis of composite support and surrounding rock and make optimal analysis of design parameters and supporting time of supporting structure, it also has important significance to improve safety and economy of the project.The Hou-Yun-Tai-Shan road tunnel at Lianyungang is the engineering background of the paper. After the interaction mechanism of surrounding rock and support system and the analysis theory of surrounding rock stability is summarized and analyzed, the numerical simulation of excavation and support processes of multi-cases tunnel is made. Contents and resulting achievement of this paper are as follow:(1) The numerical model is made by FLAC3D. The stress field and displacement field of circular section, rectangular section, straight wall arch section and curved wall section are analyzed and compared to determine the section form of tunnel. After that, numerical analysis of unsupported excavation for surrounding rock of grade II~V in six different depth is done. The parameters of surrounding rock are according to related specifications. According to simulation results, the convergence and stress variation of tunnel inner are known, which provides evidence for design analysis of composite support.(2) According to the simulation results of multi-cases, the Longitudinal Deformation Profile (LDP) and Ground Reaction Curve (GRC) are drawn. And comparative analysis between simulation results and theoretical results are taken. It has a good accordance between these two results. The variation law that convergence ratio of excavation face varies with buried depth is summarized. According to this, time-space effect induced by excavation can be known. The LDP provides evidence for the determination of initial displacement of supporting system. After analyzing the change of plastic zone and plastic stress in different depth, we can know the damage of surrounding rock. The changes of stress concentration factor as depth and grade of surrounding rock is summarized. And the support resistance is between plastic stress and the minimum rock pressure.(3) The rock samples are taken from tunneling engineering area. After rock uniaxial compressive strength test and triaxial compression test are made, the stress-strain curve and mohr circle are drawn. According to the results, deformation and strength characteristics of the rock samples are analyzed, which can determine the physical and mechanical parameters of rock samples. These two tests establish experimental basis for numerical simulation.(4) According to the design information and rock parameters of Hou- Yun-Tai-Shan tunnel, the simulation analysis of different lengths, different intervals and different diameters of anchor are taken. The results shows that the impact on surrounding rock displacement of the three factors can be sorted as: anchor length>anchor interval>anchor diameter. The pre-design plan of support structure is simulated. The stability analysis of support structure and surrounding rock is made based on the interaction analysis of composite support and surrounding rock. The safety evaluation is summarized and the result shows that the tunnel has good stability and the structural safety meet the design requirements.