Influence of ultra-close undercrossing shield on deformation of existing tunnels
摘要
With continuous development of urban construction in recent years, many Chinese cities have successively developed and increased the construction of urban rail transit projects, and the construction of the metro engineering causes surrounding surface settlements and formation deformations from time to time. Based on a shield tunneling project in Nanjing, the influence of shield tunnelling on the existing tunnel structure is analysed by site monitoring and numerical simulation. The deformation law caused by the surrounding soil of shield construction is summarized, which can provide reliable experience for subsequent projects. The results show that the ground subsidence is small when the shield is near the tunnel by the measured and simulated values. The lateral wall of the tunnel moves toward the pit in the generally horizontal direction, and the vertical displacement variation of the floor of the existing tunnel structure is greater than the settlement variation on the central axis of the roof, which mainly depends on the specific position of the shield tunneling. In the process of shield tunneling, it has a significant influence on the uplift pile of the tunnel, and the driving pressure of shield tunneling should be adjusted dynamically in time. The maximum settlement is located directly above the center of the shield double line and shows a V-shape.