Study of On-Site Monitoring Analysis and Protective Measures for Long-Distance Parallel Excavation and Underlying Metro Tunnels

With the acceleration of urbanization, the development and utilization of underground space have become increasingly common, leading to growing concerns about the impact of long-distance parallel excavation of deep foundation pits on underlying subway tunnels. This paper focuses on a foundation pit project where the parallel distance between the excavation area and the subway tunnel reached 270 m, using a combination of field monitoring and numerical simulation to analyze the deformation characteristics of subway tunnels during long-distance parallel excavation. The research results indicate that, with the increase in parallel distance, both vertical and horizontal displacements of the tunnel significantly increase. Furthermore, the “hardening soil” constitutive model achieved great simulation accuracy in modeling the deformation behavior of the soil surrounding the tunnel. Subway tunnel deformation control can be approached from three aspects: offsetting the additional stress load, improving the soil stiffness, and reducing the overall additional stress load. This study provides data support for further research on the impact of such extreme conditions on subway tunnels and offers a reference for designing and constructing similar engineering projects.