A case study of the response of support structure and stratum deformation caused by deep foundation pit excavation in soft area

Investigating the spatial distribution and evolution patterns of deformations during foundation pit excavation is crucial for safeguarding the surrounding environment. This study focuses on a deep excavation case in Nanjing and discusses the strata deformation and the response of the retaining structure through the excavation phase, informed by on-site monitoring data. A three-dimensional finite element model of the excavation was developed, with comparisons between predicted values and on-site deformation monitoring data underscoring the accuracy of the numerical simulation results. This analysis delved into the deformation spatial distribution within the retaining structure and ground surface settlement throughout the excavation. Moreover, the three-dimensional deformation patterns of the diaphragm wall at various excavation depths were scrutinized, mapping the evolution pattern and spatial distribution of ground surface settlement around the foundation pit across different excavation stages. The findings reveal a pronounced spatial effect in both the diaphragm wall deformation and ground movements behind the wall, with the greatest deformation manifesting near the symmetric plane of the excavation center and markedly less deformation near the excavation corners. Furthermore, the deformation scope broadens with increasing excavation depth. These research outcomes aim to furnish a substantive reference for practical engineering implementations.