Development of surface settlement under the combined effect of foundation pit dewatering and excavation: Insights from experimental modelling

Abstract

To investigate surface settlement under the combined effect of foundation pit dewatering and excavation, a series of experiments was conducted using a scaled model of a deep foundation pit at a metro station. During experimental simulations of the dry excavation and dewatering processes, data were collected on surface settlement, water heads outside the pit, and deflection of the diaphragm wall. The characteristics of surface settlement were compared and analyzed under different conditions with a focus on the development of surface settlement during dewatering and excavation at key locations outside the pit. The combined effect of dewatering and excavation was found to increase surface settlement outside the pit and expand its area of influence. The insertion ratio of the diaphragm wall (n) significantly affected surface settlement; as the insertion ratio increased, surface settlement, along with its area of influence, decreased. For n < 1.25, the area beyond twice the excavation depth was considered a minor area of settlement influence. In contrast, for n ≥ 1.25, this area wasn’t classified as a minor area of settlement influence. As excavation depth increased, the surface settlement pattern outside the pit transitioned from triangle-type to groove-type, groove-type settlement occurred when A_s ≥ 1.6A_c, whereas triangle-type settlement occurred under other conditions (A_s represents the area of the deep inward part of the convex deformation of the diaphragm wall; A_c refers to the cantilever part of the diaphragm wall). This study provides insights into the development of surface settlement during dewatering and excavation and serves as a valuable reference for innovations in sustainable and resilient underground design.

Keywords

Foundation pit dewatering / Deep excavation / Sustainability / Surface settlement / Laboratory test / Insertion ratio

Data availability

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

CRediT authorship contribution statement

Kai-Fang Yang: Writing - original draft, Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Min-Liang Chi: Writing - original draft, Validation, Methodology, Investigation, Formal analysis, Data curation. Chang-Jie Xu: Writing - review & editing, Supervision, Resources, Project administration, Formal analysis, Conceptualization. Chao-Feng Zeng: Writing - review & editing, Methodology, Investigation, Data curation. Lu-Ju Liang: Writing - review & editing, Validation, Methodology, Investigation. Zhi Ding: Writing - review & editing, Methodology, Formal analysis, Data curation. Ya-Shi Qiu: Writing - original draft, Methodology, Investigation, Formal analysis, Data curation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported by the National Key Research and Development Program of China (Grant No. 2023YFC3009400) and the National Natural Science Foundation of China (Grant Nos. 52508413, 52238009, and U1934208). Finally, we deeply appreciate the warm and efficient work of editors and reviewers.

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