Numerical Simulation Analysis of Stress-Seepage Coupling in Surrounding Rock of Loess Tunnels under Water Migration

This paper relies on the Tuanjie Tunnel project of the Tongwei-Dingxi Expressway, employing field monitoring, laboratory experiments, and numerical simulations to establish a coupled numerical model of the stress-seepage field for the shallow-buried segment of loess tunnels. The study analyzes the seepage-stress field in loess tunnels, it reveals the variation patterns of pore water pressure around the tunnel and the deformation of surrounding rock during construction while considering the impact of water migration. The results indicate that when the groundwater level is 10 meters from the tunnel crown, the pressure of pore water at various measurement points follows an order of tunnel invert > arch springing > arch waist > arch haunch > tunnel crown. Within the pipe roof reinforcement zone, pore water pressure increases with distance from the tunnel perimeter, while above the zone, it decreases with distance. When considering water migration, excavation of the upper bench significantly impacts the vertical effective stress at all points. Based on these insights, addressing the challenges encountered during the construction of water-rich loess tunnels, the implementation of pipe roof reinforcement measures for surrounding rock has played a positive role in enhancing the stability of loess tunnels during construction.