Abstract: In recent years, with the development of high-rise buildings and the underground space utilization, the number of deep excavation projects in China is increasing, especially in the large cities, where the subway network is dense, the construction of foundation excavation has a great impact on the surrounding environment. Reasonable measures shall be taken to protect adjacent structures and utilities from damage. This paper presents a case history of a deep excavation project of Tianyin Mansion, which is close to the Subway Line No. 2 tunnel. A three-dimensional nonlinear numerical analysis model of the interaction between the tunnel soil mass and the deep excavation support structure is established by using the finite element software MIDAS GTS NX. The deformation of the deep excavation support structure and subway tunnel in the entire process of deep excavation are analyzed. The analysis results show that the deep excavation changes the deformation field of the adjacent subway tunnels. With the increase of the excavation depth, the lateral displacement of the tunnel changes little, and the vertical displacement changes slightly. The deformation of the deep excavation support structure and the subway tunnel meet the deformation control requirements in the specifications, which proves that the interlocking pile + internal support adopted in the project can effectively control the deformation of the surrounding environment. At the same time, it also proves that the modified Mohr Coulomb model can be used to simulate the deformation of the subway tunnel caused by the excavation in complex environment.

Key words: Deep Excavation, Metro Tunnel, Numerical Simulation, Deformation, Monitoring