Numerical Analysis of the Effect of River Channel Excavation on Existing Subway Tunnels

When river channels or foundation pits are excavated above the existing subway tunnels, ground soil unloading will have a disturbance effect on the safety of the existing tunnel structure. Based on a typical river-channel excavation project, this paper designs a total of 25 comparison schemes considering the influence of five major factors: the relative distance between the river channel and the existing tunnel, river-channel excavation width, tunnel's embedment depth, grouting reinforcement thickness and grouting reinforcement range. This paper conducts a numerical simulation study on the river-channel excavation above the existing subway tunnels under different working conditions, and carries out comparative analysis on disturbance effect laws of different working conditions on deformation of the ground soil and the existing tunnel structure. On this basis, this paper constructs sensitivity evaluation indexes for disturbance effect on the existing tunnels, identifies the influence sensitivity of the above five major factors, and provides engineering suggestions and measures. Finally, based on the numerical simulation results, we carried out a field verification test. The research work in this paper can provide some reference for design and risk prevention of excavation engineering adjacent to the existing subway tunnels.