The seismic response of a fabricated subway station is a complex structural connection problem that depends on the mechanical properties of the joints. In order to obtain the optimal joint distribution of a fabricated station structure under earthquake action, three finite element models of a single ring structure of fabricated subway stations assembled with seven, five, and four prefabricated components were proposed. Seismic wave characteristics, peak acceleration, and coupled horizontal and vertical seismic components were considered to study the seismic response of the fabricated subway station structure with different forms of the joint distribution. The dynamic time history method was used to analyze the seismic response in three aspects: structure plastic strain, interlayer relative deformation, and internal force. The damage indexes and residual strength indexes of the joints were offered based on the concrete damage index to evaluate the joints’ damage degree. The results showed that the joints of the vault or bottom plate had little influence on the seismic response of the fabricated station structure. The sidewall joints had the obvious seismic response and the most severe damage under horizontal ground motion or coupled ground motion, which were the weak joints of the fabricated station structure. The existence of vertical ground motion aggravated the damage degree of sidewall joints, making the damage occurrence time of sidewall joints earlier and the damage end time extended. On the premise of meeting the mechanical load and site requirements, an assembly scheme with fewer prefabricated components can be selected.

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.

Under the circumstance of soft fractured surrounding rock with high geo-stress, the support technology of tunnel has become a major challenge. Traditional I-shaped steel and bar lattice girder, which cross-sections are often designed to be left-right symmetrical, may have insufficient strength and stiffness. Based on the concept of symmetry, a new support technology of spatial steel tubular grid (SSTG) arch is designed with high strength and large stiffness. In order to clarify the mechanical properties and failure mechanism of SSTG arch used as primary support, through laboratory and numerical experiments, this paper carries out the bending tests for the circumferential joint of SSTG arch components combined with the excavation tunnel project of Panyu Square Station in Guangzhou, and the analyses of the ultimate bearing capacity, deflection displacement, failure modes, and stress–strain evolution laws of joint components are conducted in detail. The results show that during the whole process of loading, the arch components have experienced elastic growth stage, plastic development stage, and final failure stage. The average ultimate bending capacity of SSTG arches is 340.5 kN·m, and the joint opening is 13.9 mm. The joint form of high-strength bolt + rigid flange plate proposed in the paper has reasonable stress state and high safety redundancy, which can bear the load of surrounding rock effectively, and ensure the safety in tunnel construction. The research results could provide a theoretical basis for the design and application of SSTG arch support in related projects.

In open-cut assembled subway tunnels, foundation pit enclosure piles are typically cast in place. However, this conventional approach limits the functionality of the piles to serving as retaining structures during excavation, resulting in resource inefficiency and the underutilization of prefabrication techniques. To address this issue, a fully prefabricated pile-wall composite scheme is proposed for cut-and-cover tunnels to optimize the retaining effect of the piles and leverage the benefits of prefabricated technology. In this scheme, the retaining pile and lining are both prefabricated. The pile is the temporary retaining structure during pit excavation and a part of the sidewall. This scheme was researched and applied in Jinan, China. Field monitoring and numerical simulation were used to investigate the load transfer within the fully prefabricated pile-wall composite structure (PPWS) and its mechanical response, respectively. The results show: (1) The development of lateral earth pressures on the PPWS experienced three stages. The lateral earth pressure distribution indicates that the PPWS can fully activate the retaining effect of precast piles. (2) Following the backfilling of the joints, the horizontal displacement at the bottom of the precast pile reduced by 0.39 mm. Numerical simulation results indicate the effectiveness of precast pile restraint in PPWS. (3) The PPWS exhibited uniform deformation transition at the joints. The joints play a crucial role in coordinating deformation between the precast piles and sidewalls, utilizing the restraining effect of the precast piles.