Deformation analysis and safety assessment of existing metro tunnels affected by excavation of a foundation pit

摘要

The excavation of a foundation pit considerably affects the adjacent structures and underground pipelines owing to the change in the stress state of the surrounding soil, resulting in deformation. The study of an actual engineering case was conducted to examine the influence of excavation on the deformation of adjacent subway tunnels. The finite element analysis software PLAXIS 3D was used to simulate the entire excavation process. The structural design of the foundation pit was optimized based on the simulation results to ensure the stability of the foundation pit and the safety of the existing subway tunnel structure. Finally, the safety evaluation of the excavation of the foundation pit that caused the deformation of the adjacent subway tunnel was performed. The influence of the excavation and unloading of the foundation pit on the subway tunnel is closely related to the distance between the subway and the foundation pit, the amount of earthwork excavated at one time, and the engineering geological conditions. The results of this paper can provide useful reference for the design optimization and safety assessment of similar projects.