Analysis of Rock Mass Parameters and Plastic Zone of a Tunnel in Southwest Mountainous Area

The deformation damage and support difficulties caused by the formation and expansion of plastic zone of surrounding rock have always been urgent engineering problems to be solved, especially in areas with prominent non-uniform stress fields. Choosing a reasonable and practical method to determine the plastic zone is of great significance for ensuring the long-term stability and safety of tunnels. Based on a tunnel project in the southwest mountainous area, this paper conducted mechanical tests to obtain the mechanical parameters of granite. The analytical method optimized based on the principle of stress balance was applied, and the numerical simulation was carried out according to the field displacement monitoring data and experimental parameters, the plastic zone of the medium quality granite cross-section and fault fracture zone granite cross-section was analyzed comprehensively. The results shown that the analytical and numerical solutions are in good agreement with engineering practice. It proved that the theory and method in this paper are scientific and practical in engineering. The research results can provide support for the design optimization and construction safety of the tunnel, and the research ideas and methods can also provide reference for similar projects.