Ground Settlement and Mechanical Response of a Deep Excavation in Soft Soils: A Field and Semi‐Analytical‐Based Case Study in Shenzhen, China

ABSTRACT The construction of deep excavation inevitably impacts the surrounding strata, posing risk to the safety of adjacent buildings. Therefore, accurately evaluating strata settlement during the construction is essential. This study considers Shenzhen Metro Chegongmiao Station as a case study, offering a comprehensive analysis of the mechanical behavior throughout the entire deep excavation process. A predictive method is proposed, incorporating the Mindlin solution and the Source‐Sink Imaging method. This method includes simplified representations of the unloading effects from diaphragm wall construction and soil excavation. Additionally, nonlinear fitting is employed to derive the dewatering curve, addressing the challenge of predicting the groundwater level outside the excavation zone. The influence of the dewatering is thus quantified through calculating the seepage volumetric forces. The results demonstrate that in water‐rich strata, the unloading effect due to diaphragm wall construction‐ a factor frequently underestimated in conventional analysis‐ exerts a profound influence on the surrounding strata. Quantitative evidence from the case study reveals that this phase alone contributed 12 mm to the surface settlement, accounting for a significant 44% of the cumulative displacement (27 mm). The settlement curves exhibit variations across different construction stages. Notably, the location of the maximum surface settlement during the diaphragm wall trenching occurs at the point farthest from the excavation. Furthermore, an analysis of the factors influencing settlement shows that slurry density has the most substantial effect. With the same relative change, slurry density exerts an influence on settlement that is up to 30 times larger than the effects of other variables. These findings provide a scientific foundation for the design, construction, and safety assessment of deep excavations in water‐rich strata.