# Research on Construction Sequencing and Deformation Control for Foundation Pit Groups
## 1 Introduction
[11], via the Wuhan case numerical simulation, found that deep foundation pit excavation can cause adjacent tunnel structures to have additional bending moments and shear forces, with the influence range positively related to soil parameters and excavation depth. [PERSON] et al [12], for the Beijing elevated bridge foundation pit project, proposed that pier displacement control requires real-time monitoring and dynamic support scheme adjustment to lower track structure deformation risk. In soft soil foundation pit deformation characteristics and sectional excavation, [PERSON] et al. [13], taking the Hangzhou soft soil foundation pit as an example, pointed out through numerical analysis that large-scale sectional excavation can greatly cut overall foundation pit deformation, yet sectional sequence optimization is needed to balance supporting structure forces. [PERSON] et al. [14], based on the Nanjing case, proposed that in soft soil foundation pit excavation, the Hardening Soil Small-Strain (HSS) model can more accurately simulate surrounding soil deformation, and soil reinforcement in the active zone is more effective for deformation control than that in the passive zone. Based on new technology and intelligent monitoring, [PERSON] et al. [15] developed a digital twin intelligent monitoring system, solving traditional methods' inability to predict risks in real time. Its data-driven model updates have greatly improved deformation prediction accuracy. [PERSON] et al. [16] put forward the capsule grouting expansion technology simplified theory, offering a quantification tool for pile foundation deformation control. The combination of virtual images and finite difference method in their approach can accurately predict grouting effects. Existing research on foundation pit groups has predominantly focused on case-specific optimizations of construction schemes, with limited attention to the mechanical interactions between adjacent retaining structures [17; 18; 19]. While numerical simulations and field measurements are widely employed, their effectiveness is constrained by parameter sensitivity and operational complexity [20; 21], respectively. Laboratory model tests [22], particularly cost-effective scaled models, offer controlled insights into deformation patterns but remain underutilized for analyzing multi-pit configurations. Current urban projects increasingly involve adjacent or segmented pits [19; 23; 24], yet systematic investigations into stress redistribution mechanisms under varying construction sequences (e.g., deep-to-shallow vs. synchronous excavation) and spacing effects (e.g., B/He thresholds) are lacking. This gap hinders the development of practical guidelines for mitigating deformation risks in spatially constrained environments, necessitating a comprehensive approach to unravel the interplay between excavation strategies and geotechnical behavior. In pit group projects, the excavation sequence and spacing (B/He ratio) of adjacent pits significantly affect the deformation and stability of retaining structures. In dense urban areas with complex geology, narrow spacing can cause soil stress overlapping, worsening mutual structural disturbance [25; 26]. Different excavation sequences also influence stress redistribution by altering soil unloading paths. The main research gaps are as follows: First, the critical threshold of pit spacing has not been quantitatively analyzed, making it hard to design safe spacing under different geological conditions. Second, excavation sequence optimization relies too much on engineering experience, causing uncertainty in deformation prediction and construction planning for complex pit groups. To address these gaps, this study integrates physical model tests and PLAXIS 3D numerical simulations. Section 2 details the experimental methodology, including scaled model design, instrumentation, and constitutive model selection (HSS model).