Optimization Analysis of Isolation Pile Parameters for Rail Transit Foundation Pits near High-speed Railway Pile-slab Subgrade

Abstract

[Objective] Deep foundation pit construction adjacent to high-speed railway subgrades can adversely affect the stability of existing subgrade structure. As a commonly used protective reinforcement measure in engineering practice, isolation piles installed outside the foundation pit can effectively control the deformation of the surrounding environment caused by foundation pit excavation. Therefore, studying the influence of isolation pile design parameters on foundation pit deformation control is of great significance. [Method] Based on the construction of No.1 ventilation shaft excavation for Shanghai Suburban Railway Airport Link Line, numerical simulations are conducted using finite element software. Five key design parameters are selected including isolation pile length, distance from the underground diaphragm wall, pile spacing, pile diameter, and pile stiffness. An orthogonal experimental design method is employed to construct 18 working condition combinations. The control efficiency of isolation piles on the horizontal displacement and settlement of high-speed railway pile-slab subgrade bearing slabs, as well as the horizontal displacement of pile top, and the amplification efficiency of the maximum horizontal displacement of the above pile-slab subgrade piles are used as evaluation indicators. The influence of each design parameter on subgrade deformation is quantitatively analyzed, and optimization recommendations for isolation pile design parameters are proposed. [Result & Conclusion] Isolation piles can not only effectively control the horizontal displacement of shallow subgrade pile foundation, but also amplify the horizontal displacement of deep subgrade pile foundation. The distance between isolation piles and underground diaphragm wall significantly affects all evaluation indicators. To ensure the safety of adjacent high-speed railway subgrade, it is recommended to appropriately increase the distance between isolation piles and underground diaphragm wall.

Keywords

• rail transit
• foundation pit
• isolation pile parameters
• high-speed railway pile-slab subgrade