Numerical analysis of a deep and oversized group excavation: A case study

Abstract

Group excavations are composed of several individual excavations adjacent to each other with simultaneous or successive construction sequences (CS), which are distinctive from individual excavation in terms of the performance of excavation. In this study, a hyper-scale 3D finite element model was established to investigate the deformation behavior of a diaphragm wall system retaining a deep and oversized group excavation (DOGE) in Shanghai soft clay deposits. The numerical model simulated the practical construction stages and sequences, and it was verified by a series of comparisons with field measurements. Based on the numerical model, the spatial effect of the performance of DOGE in the process of excavation stages was investigated in this study, which cannot be addressed by limited field measurements. Furthermore, the effects of partition walls and CS on the deformation control were discussed to provide practical suggestions for oversized and deep excavations. The results indicate that the employment of bi-partition walls to divide the oversized excavation into several small pits and mono-partition walls and cross walls to further divide the pits near the metro lines into smaller ones, was proved to have significant effectiveness in controlling the wall deflection and protecting the adjacent metro line. For the partition wall, the magnitude and direction of the wall deflection primarily depended on the initial excavation, while the influence of subsequent excavation activities proved insignificant. Thus, it should be noted that the effect of the initial excavation should be especially concentrated. The findings can help optimize similar DOGE engineering.

Keywords

Excavation / Deformation behavior / Numerical simulation / Structural interaction / Spatial effect

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonablerequest.

CRediT authorship contribution statement

Mingguang Li: Writing – review & editing, Writing –original draft. Haobiao Chen: Software, Investigation. Zhongjie Zhang: Writing – review & editing. Jinjian Chen: Supervision, Projectadministration.QirunYang:Validation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that couldhaveappearedtoinfluencetheworkreportedinthispaper.

Acknowledgement

This work was supported by the National Natural Science Foundation of China (Grant No. 52278361), the Science and Technology Commission of Shanghai Municipality (Funding No. 22DZ1202904), and the Natu-ral Science Foundation of Shanghai (Grant No. 22ZR1430800). The authorsaregratefultotheseprograms.Specialthanksalsogototheanonymouspeerreviewers,whosecommentsgreatlyimprovedtherigorousnessandqualityofthispaper.

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