Deformation Characteristics and Optimization Design for Large-Scale Deep and Circular Foundation Pit Partitioned Excavation in a Complex Environment

With the rapid development of urban rail transit, the impact of the construction of large-scale deep and circular foundation pits (LDCFPs) on the surrounding environment has become increasingly prominent; however, there is no definite standard for the design theory and construction method of the retaining structure of LDCFPs; therefore, the such standard needs further research and exploration. The paper is based on the LDCFP engineering of a subway station in Wuhan, China. Two partitioned excavation methods (step-by-step and synchronous excavation) of LDCFP were discussed by numerical simulation; the deformation characteristics of the soil around the foundation pit, the lateral deformation of the retaining structure in each partitioned district, and the distribution of the supporting axial force were analyzed; the deformation law of LDCFP was revealed; and the safe and economic excavation method was determined. The field monitoring test was carried out to reveal the deformation characteristics and stress evolution behavior for the supporting structure of the LDCFP in the subway station. It was concluded that the construction method of synchronous partitioned excavation in the same layer is more conducive to controlling the overall deformation, with the deformation of the circular retaining structure being uniform and the “vault effect” of the circular retaining structure having a certain constraint on the deformation of the foundation pit. The research results can provide guidance for the design and construction of supporting engineering and similar engineering.

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