Simplified Calculation Method of Wall–Brace Coordinated Deformation in the Excavation Process of a Foundation Pit under Multifactor Coupling

This paper proposes a coordinated deformation calculation method for foundation pit engineering to improve deformation control between underground diaphragm walls and supports. The study validates the practicality of the coordinated deformation formula through actual engineering applications and simulation analysis, making it particularly suitable for foundation pit calculations with external overloads or additional loads caused by outer pit slopes. Finite-element software PLAXIS 3D (version 2022) is used for simulation, with the soil modeled using the hardening small strain constitutive model. When considering support positions and construction sequences, the calculations found that supports placed near the top of the wall and early installation of supports are more effective in controlling deformation. Additionally, the calculations show that the slope height of the outer pit, and the relative position between the outer and inner pits, significantly affect the deformation of the inner pit support structure. The smaller the outer pit slope height and the greater the distance from the outer pit to the inner pit, the less deformation occurs in the underground diaphragm wall. This method simplifies the calculation process and is applicable to various foundation pit excavation projects.