Analysis of Deformation Characteristics of Deep Foundation Pit in Urban Rail Transit Station under Unbalanced Load

Abstract

[Objective] At present, the underground engineering diseases and accidents caused by unbalanced load in urban rail transit are increasing gradually. In order to understand the adverse effect of unbalanced load on the deformation of deep foundation pit in urban rail transit station and reduce the construction risk, it is necessary to analyze the deformation characteristics of station deep foundation pit under unbalanced load. [Method] Based on theoretical analysis and on-site monitoring data, the aforementioned deformation characteristics are studied, the changing law regarding the retaining pile deformation, the horizontal displacement of the deep soil and ground settlement is analyzed, and the interrelation between the retaining pile deformation and the deep soil horizontal displacement, the ground settlement and excavation depth is discussed. [Result & Conclusion] The horizontal displacement curve of the retaining pile is fish-belly shaped, and the formation condition has obvious influence on the deformation of the retaining pile. There is a roughly linear relationship between the deformation of the retaining pile and the horizontal displacement of deep soil, and the empirical coefficient is proposed to be 1.30. Due to partial load, the ground settlement around the deep foundation pit is larger, and the relationship between the maximum horizontal displacement δhm of the retaining pile and the maximum ground settlement δvm is δvm=(0.9~3.0) δhm, and the proportional coefficient between them is greater than the value under symmetric load. The strong deformation resistance of rock strata limits the deformation of the retaining pile. There is a relationship of δhm=(0.009%~0.060%) He between δhm and He, and the proportional coefficient between them is smaller than the value under symmetric load. The impact area of deep foundation pit construction on the surrounding environment is mainly divided into Zone 1 (main impact zone), Zone 2 (secondary impact zone) and Zone 3 (no impact zone), and the impact area of foundation pit construction is about (0~2.5) He.

Keywords

• urban rail transit
• station
• deep foundation pit
• deformation characteristics
• unbalanced load