Study on Development Characteristics and Movement Process Numerical Simulation of the slumping deposit above Haojiping Tunnel Entrance

Abstract

The stability of railway tunnel entrance slopes directly affects construction and operational safety. Taking the slumping deposit above the entrance of Haojiping Tunnel on the Shanghai–Kunming High-Speed Railway as the research object, the development characteristics of the mass and the damage to existing protective measures were identified through field investigation. The three-dimensional movement process following potential failure was simulated using DAN3D software, and the slope stability under different rainfall conditions was analyzed using GeoStudio software. Targeted prevention and control recommendations are proposed. DAN3D simulations indicate that after failure, the mass movement lasts approximately 40 s, with a maximum horizontal travel distance of 78.1 m and a maximum velocity of 14.5 m/s. The maximum accumulation thickness reaches 1.3 m, posing a threat to the railway line at the tunnel entrance. GeoStudio calculations reveal a stability factor of 1.110 under natural conditions, corresponding to a basically stable state. Under a cumulative rainfall of 270 mm over three days, the factor decreases to 1.013 (under-stable state), and under an extreme rainfall of 360 mm over three days, it drops to 0.953 (unstable state). This confirms that short-duration intense rainfall is the primary trigger for potential failure of the creeping landslide mass. Based on the analysis, it is recommended to install additional passive protective nets, strengthen deformation monitoring, and regularly clear drainage facilities to ensure railway operational safety. The research findings can provide a theoretical basis for the operation and maintenance of railway tunnels in the hilly and mountainous regions of South China.