Cause Analysis and Countermeasure Study on Significant Deformation of Chengdu Metro Foundation pit Retaining Piles

Abstract

[Objective] The complex environmental and geological conditions surrounding metro foundation pit construction can easily lead to accidents. It is necessary to analyze the reasons for significant deformation of foundation pit retaining piles and propose targeted reinforcement measures. [Method] Taking a metro station foundation pit of pile-anchor supporting structure adjacent to old buildings in Chengdu as engineering background, the causes of significant deformation of the retaining piles during foundation pit construction are analyzed and reinforcement measures to control pile deformation are proposed. Using the Harding-soil second-order advanced constitutive model, the feasibility of following measures after retaining pile deformation such as counter-pressure surcharge within the pit, steel pipe piles for the outer slope of the pit, and reinforcement with two additional anchor cables before re-excavation are studied. [Result & Conclusion] Simulation results and field measurements indicate that the accumulated displacement of the retaining piles is 77.77 mm. After implementing reinforcement measures following significant deformation, the horizontal displacement of the retaining piles can be controlled within 53 mm. The consistency between the simulated and field-measured results of the pile horizontal displacement curve change law is evident. Actual construction results demonstrate that the deformation control effect of the foundation pit is significant after adopting reinforcement measures, with no widespread deformation occurring in subsequent construction processes.

Keywords

• metro
• foundation pit
• retaining pile deformation
• pile-anchor support