Numerical Analysis of Ground Settlement of Close Buried Double-Line Shield Tunnels Under Different Excavation Conditions

Construction-induced mutual disturbance exerts a substantial influence on the ground settlement of double-line tunnels, and the ground settlement of double-line tunnels differs under varying excavation conditions. This study deeply analyzes the ground subsidence of a near-buried double-line tunnel when excavating in a complex geological environment. This study provides a framework for the design and construction of double-line shield tunnels and makes up for an important gap in the existing research. The findings indicate that the construction of post-excavation tunnels leads to secondary disturbances in the soil, resulting in increased ground settlement. The influence of tunnel lateral spacing on ground subsidence is greater than that of longitudinal excavation spacing. The ground settlement of a double-line tunnel excavated concurrently exhibits an initial increase, subsequently reaching a stable state as excavation progresses. For double-line tunnels with different excavation intervals, the settlement curves exhibit three stages. The maximum horizontal deformation of double-line tunnels decreases with increasing tunnel space, and the horizontal deformation of continuously excavated double-line tunnels is greater than that of synchronously excavated double-line tunnels. The incorporation of the settlement ratio, S’, unveils a linear correlation between the settlement and the tunnel space.