Post-construction Foundation Pit Design at Interchange Hub and Impact Analysis on Surrounding Environment

［Objective］ The excavation work for the subsequent foundation pit at interchange hub area faces technical challenges such as highly sensitive surrounding environments, complex project boundary conditions, numerous construction constraints, and significant difficulties in protecting existing structures. Therefore, it is essential to analyze the design plan for the subsequent foundation pit at the interchange hub and its impact on the surrounding environment in depth. ［Method］ Using an open-cut underground space engineering project of high-speed railway and metro interchange hub located in deep silty soil layers for case study, the overall design scheme of the foundation pit is introduced. Finite element software is used to perform a 3D numerical simulation of the entire construction process, evaluating the potential impact of underground space construction activities on the surrounding existing structures. The simulation results are then compared with on-site monitoring data to verify the reasonableness of the design plan and systematically summarize the experiences gained during the design process. ［Result & Conclusion］ It needs to fully consider surrounding environmental conditions for the foundation pit project in the interchange hub area, the layout of individual buildings and excavation depth, coordinate the involved construction units, and prioritize the adoption of a co-construction plan to reduce temporary engineering work and maximize the interests of all parties. TRD (trench-cutting re-mixing deep wall method)+inserted steel bracing system performs excellently in water retention, and is suitable for foundation pit projects with moderate depth, thick permeable layers, complex surrounding environments, and stringent water retention requirements, where the water curtain must extend to the impermeable layer. Furthermore, the subsequent foundation pit construction at interchange hub should be fully integrated into the protection scope of the previously constructed individual buildings. Through scientific segmentation and excavation sequencing, the adverse impact on existing structures can be effectively mitigated.