Objective The excavation of a newly built tunnel causes the stress release of surrounding soil, subsequently altering the attitude and inducing displacement of the existing tunnel, which threatens its structural health. Therefore, it is imperative to study the attitude response of the existing tunnel and the influence range of the newly built tunnel.

Method Taking a shield tunnel section between Yushan Square Station and Zhujiang Road Station on Suzhou Metro Line S1 as an example of an existing tunnel structure, the displacement control method is employed to control the ground loss during new tunnel construction. Analysis and discussion are conducted according to different crossing modes and convergence modes of the newly built tunnel, as well as varying clearances between the new and existing tunnels. The response characteristics of the existing tunnel structure are analyzed using finite element numerical simulation technology.

Result & Conclusion  In under-crossing scenarios, the displacement and deformation of the existing tunnel exhibit a monotonic relationship with the clearance. The vertical displacement of the existing tunnel increases as the clearance decreases, while the range of the deformation section decreases as the clearance decreases. In over-crossing scenarios, the vertical displacement of the existing tunnel shows a non-monotonic relationship with the clearance. Additionally, the horizontal convergence of the new tunnel excavation face exerts a certain influence on the vertical displacement and the minimum longitudinal curvature radius of the existing tunnel. In both over-crossing and under-crossing scenarios, the minimum longitudinal curvature radius of the existing tunnel should be taken as a structural safety evaluation index. For under-crossing scenarios, the clearance should be controlled more than 0.9 times the tunnel diameter, while for over-crossing scenarios, it should be controlled more than 0.5 times the tunnel diameter.