Abstract: Due to the influence of tunnel excavation disturbance and rainfall infiltration, the deformation and stability of a tunnel entrance slope of the expressway have always been the focus of safety construction. The case history of the deformation and failure of a high-speed tunnel entrance slope in Guangxi is presented in this paper. Throughout the on-site geological hazard investigation, the main stratigraphic lithology and geological structure of the tunnel entrance slope, slope cracking and deformation, tunnel collapse and other characteristics are obtained and well understood. Combined with the monitoring data, the main influencing factors of the deformation and failure of the object project are proposed. The numerical simulation is used to reproduce the deformation and failure process of the tunnel entrance slope induced by rainfall. The range of deformation and failure, development and evolution process and safety factors are analyzed, and compared with the field failure mode observed. It is considered that the deformation and failure process is tunnel excavation-slope deformation-critical failure-rainfall infiltration-slope weakening-joint tension slip-slope deformation and failure-additional external force-tunnel collapse and roof fall.

Key words: Tunnel Entrance Slope, Deformation and Failure, Rainfall, Joint Fissure, Numerical Simulation