Traditional support structures cannot meet the complex conditions of different excavation depths and areas in underground transportation hubs. On the basis of fully considering the spatial position relationship of foundation pit groups, this article proposes a multilevel retaining system that meets the requirements of multilevel foundation pit excavation. The evolution law of the support structure during the excavation process of the inner pit was explored using on-site monitoring and numerical simulation methods. The results indicate that the excavation of the inner pit reduces the passive earth pressure, and the deformation of the outer support structure can be effectively suppressed by setting a retaining structure or a bottom slab in the bench zone. The excavation of the inner pit causes significant vertical deformation of the support structure adjacent to the foundation pit, while the impact on the structure far away from the foundation pit is relatively small. According to the contact force chain and soil pressure between the two rows of support structure, the soil in this area is divided into a “relaxation zone” and a “compression zone.” The evolution mechanism of earth pressure in the case of mutual-effect failure between two rows of piles is revealed. This paper addresses the deformation properties of multilevel support structures as well as the mechanism of earth pressure evolution between structures.

To solve the impact on the pre-existing main structure due to the need for early traffic restoration of urban roads within the cross-hub and the difficulty of co-ordinating a construction plan among groups of pits, a construction method combining TD and BU was proposed. By establishing a three-dimensional finite difference method (FDM) of parallel pit excavation considering the small strain constitutive model of the strata, the influence of four different excavation schemes on the pre-existing main structs is studied. The results of the study show that: (1) the asynchronous excavation of the pit on both sides of the cover excavation area causes additional deformation of the steel pipe structs; sequential excavation produces the greatest additional deformation of the steel tube columns, followed by staggered excavation and the least simultaneous excavation; (2) the middle 1 slab enhances the overall stiffness of the main structure in the cover excavation area, reducing the additional deformation caused by the unsynchronized excavation of the pit, with the maximum horizontal deformation of 5.8 mm, a reduction of 61%; (3) the greater the depth of excavation and the closer the distance from the pit, the more obvious the deformation of the steel pipe column; and (4) the function relationship between δ_hm/H and the relative stiffness coefficient R_d was obtained by fitting, and the maximum controlled mis-step spacing of the foundation excavation on both sides was 4.3 m when the middle 1 floor slab was cast.