Analysis of Deformation Effect of Underpass Cross Tunnel Caused by Foundation Pit Excavation

Taking the transfer hall project of a subway station as an example, FLAC^3D numerical simulation software was used to analyze and summarize the influence law of the excavation of the deep excavation of the upper span on the deformation of the underpass three-dimensional cross tunnel with different spatial distances and distribution forms. Combined with the field monitoring data and the mutual verification of the numerical simulation results, the results showed that: (1) The effect of excavation unloading on the structural deformation of the tunnel is mainly manifested as vertical displacement, and its deformation is closely related to the spatial position of the foundation pit and the unloading amount of the rock-soil mass of the foundation pit; (2) The monitoring data of the whole construction cycle of the left and right tunnels of Line 1 are in good agreement with the numerical simulation results, which verifies the accuracy of the judgment of the influence of the numerical calculation method on construction activities; (3) The vertical displacement of the cascade tunnel coupled with multiple stress states is significantly affected by superposition effect, and the maximum vertical displacement is located in the area with many influencing factors, and the maximum vertical displacement is 34. 84 mm; (4) Tunnels with shallow burial depth are more sensitive to construction disturbance than those with deep burial depth. The deformation dispersion at different locations is stronger, and the deformation has certain integrity and coordination.