Water Disaster Susceptible Areas in Loess Multi-Arch Tunnel Construction under the Lateral Recharge Condition

The water disaster susceptible areas in loess multi-arch tunnels were studied. Taking Lishi multi-arch tunnel as an example, the tunnel is located in Luliang City, Shanxi Province, China, with a total length of 180 m. It is the first loess multi-arch tunnel in China. The groundwater recharge in the tunnel site is dominated by rainfall, and the surrounding rock of the tunnel is unsaturated. Considering the lateral recharge of groundwater, in this study, midas geo-technical analysis system was adopted to simulate the construction process of a middle pilot tunnel-bilateral pilot tunnel of a loess multi-arch tunnel, accounting for fluid-solid coupling. The variations in the surrounding rock stress and seepage fields of loess multi-arch tunnels during the construction process were studied. A water disaster susceptible area in a loess multi-arch tunnel was confirmed based on the catastrophe area of the displacement, stress, gross head, pore water pressure, and seepage velocity. The result show that the water disaster susceptible areas for loess multi-arch tunnels during the construction period mainly concentrated in the mid-partition, arch springs of the left and right tunnels, and the tunnel face.