Research on the Effects of Pit Excavation on Adjacent Existing Subway Tunnel Structures Based on the FEM-DEM Coupling Method


== Abstract ==

With the swift advancement of underground space development, large deep excavation projects above subway stations are becoming more common. This study employs the Finite element method-Discrete element method (FEM-DEM) coupling method to examine the effects of excavation on the structure of nearby subway tunnels. First, the f lexible triaxial compression test was conducted using the FEM-DEM coupling method to acquire the macroscopic mechanical characteristics of various soil layers. Based on this, the ground particle model was developed using the particle size scaling method, the underground continuous wall support was constructed via the FEM-DEM coupling method, and the tunnel model was established using particles arranged circularly. The study shows that with the excavation, the particles at the bottom of the foundation start to heave upward, with the maximum uplift displacement being approximately 10 mm. Throughout the excavation process, substantial changes occur in the contact force chain within the pit, with notable stress release at the pit bottom. Moreover, the porosity at the pit bottom gradually increases, and the vertical stress decreases; the stress decreased by 75% compared to before excavation, primarily due to stress release during excavation. Lastly, a focused analysis was conducted on the tunnel deformation during excavation. Throughout the foundation pit excavation, the tunnel’s displacement mainly took place within the excavation area, and its vertical displacement increased as the excavation depth increased, with a maximum displacement of approximately 0.5 mm. Analysis of particle displacement at various locations in the tunnel revealed that particles closest to the foundation pit bottom experienced the greatest displacement, whereas those farther away had relatively smaller displacements. The findings offer crucial theoretical support for the design and implementation of excavation projects.

== Full document ==
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