###### Abstract  
Based on the complex deep foundation pit group process of the Huimin Avenue Comprehensive Reconstruction Project in Nanjing, the finite element numerical simulation method is used to analyze the deformation characteristics of the retaining structure and the coupling effect between foundation pits during the whole process of excavation and support construction of the complex foundation pit group. Meanwhile, the differences in the deformation characteristics and coupling effects of the retaining structure under different construction time sequence schemes of the foundation pit group are studied. Finally, some suggestions are put forward for the monitoring and construction in this project, which provides a reference case for the design and construction of similar foundation pit groups. foundation pit group; diaphragm wall; coupling effect; excavation sequence; numerical simulation +
Footnote †: journal: Medical  
by the semi-top-down method can restrain the displacement of the wall and the ground, as well as the lifting of the support. The lateral displacement caused by the semi-top-down construction method is much smaller than that caused by the normal construction method and the top-down construction method. The semi-top-down construction method is applicable to excavation in crowded urban environments [16]. [PERSON] et al. used numerical simulation to study the characteristics of the excavation behavior of the foundation pit by applying the prestressed support (IPS) earth retention system, and found that the IPS earth retention system can effectively reduce the lateral displacement of the foundation pit. The control of deformation was more obvious by reducing the thickness of layered excavation than by adjusting the excavation sequence [17]. [PERSON] et al. investigated the stress and deformation characteristics of a composite soil nailing wall and an anchored soldier pile wall combined retaining system. The study showed that the location of the bending moment extremes of the retaining piles was located near the excavation surface. Increasing the stiffness or burial depth of retaining piles or the pre-stressing of anchor piles can effectively control the lateral displacement of excavation, but the effect is not obvious after exceeding a certain range [18]. [PERSON] et al. studied the deformation law of a subway station foundation pit in a soft-soil area using a diaphragm wall and a multi-support system, and found that the method of excavation in sections and layers can effectively control the deformation of foundation pit support structure and reduce the impact on surrounding buildings. Increasing the insertion ratio of the diaphragm wall can reduce the maximum horizontal displacement, but when the insertion ratio is greater than 0.9, the influence of the insertion ratio on the horizontal displacement is very small [19]. [PERSON] and [PERSON] [20] proposed an evaluation method based on the minimum potential energy method to predict the deformation of the ground and the deflection of the support wall within the influence zone of the foundation pit excavation, and the comparison with the measured data was in good agreement. [PERSON] et al. conducted back analysis on the permeability coefficient of the soil layer based on the on-site pumping test, and simulated the dewatering of the foundation pit using the three-dimensional finite difference method. The results showed that the settlement amplitude of aquifer soil decreases with the increase in the depth of the diaphragm wall. The maximum ground settlement outside the foundation pit can be reduced by optimizing the drainage scheme [21]. This study analyzes the interaction and the complex deformation mechanism of each foundation pit excavation, relying on the complex deep foundation pit group of the Huimin Avenue Comprehensive Reconstruction Project in Nanjing. The foundation pit group project is part of an underground interchange construction project.