The excavation of the foundation pit will cause changes in the soil stress field around the foundation pit, and that may have adverse effects on the adjacent subway tunnels. In this paper, a complex deep foundation pit excavated in different sections is taken as the research object, and the support structure of the complex foundation pit project is introduced, which accumulates experience in the selection of support structure for similar projects. The finite element models are established by MIDAS/GTS software to evaluate the influence of excavation in different sections of the foundation pit on the tunnel deformation, and the accuracy of the finite element calculation results is verified by comparing the monitoring data. The results show that: The horizontal deformation of the subway tunnel is generally smaller than the vertical deformation. Tunnel monitoring should focus more on the development of the vertical deformation of the tunnel. The maximum vertical deformation and horizontal deformation of the tunnel are both smaller than the local specification limits, and the excavation of the foundation pit in this project has little influence on the deformation of the subway tunnel.

The effect of large deep foundation excavations on the surrounding existing tunnels is a problem that cannot be avoided in the current construction background. This effect is difficult to assess precisely, especially when the geometry of the tunnels and pits is complex. In this paper, a three-dimensional (3D) finite element model has been developed based on a case containing four complex intersecting tunnels and a large deep foundation pit. The model used the hardening soil model with small-strain stiffness (HSS) and the Hoek–Brown (HB) model to describe the mechanical properties of the soil and rock, and various methods including the standard penetration test (SPT) and heavy dynamic penetration test (HDPT) were used to determine the model parameters. The results of the analysis are as follows: the excavation of the foundation pit caused the tunnels to heave and the heave deformation conforms to the normal distribution; the maximum heave of numerical simulation is 3.1 mm which is consistent with the field data; the horizontal displacement, horizontal convergence, and vertical convergence of the tunnels caused by the excavation of the pits are small, and all kinds of deformations meet the control requirements; the intersection of multiple tunnels shows obvious stress concentration when the tunnels were constructed, and the lining stress slightly decreases as excavation progresses.

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