Study on slope instability caused by excavation of shallow buried small spacing loess tunnel

The construction time of shallow buried small spacing tunnel is long, the surface deformation is large, and the surrounding rock disturbance range is wide. The staggered excavation of double caverns will cause secondary disturbance to the surrounding rock, which is easy to cause the instability of the soil near the tunnel slope. Based on a tunnel project introduced from China-Lanzhou Passenger Dedicated Line to Lanzhou Hub, the influence of construction sequence and excavation support method on slope stability of small spacing tunnel is studied by using numerical analysis software ABAQUS, and the displacement and stability safety factor of tunnel adjacent slope under different excavation methods are analyzed by local strength reduction method. The results show that : (1) Tunnel excavation reduces the safety factor of mountain slope and causes slope instability; (2) The horizontal displacement of the slope is small and the stability safety factor is large when the construction sequence of the left tunnel is first used for tunnel construction, which is conducive to slope stability. (3) In order to reduce the disturbance of tunnel excavation on the slope, CD method should be used.