Deformation characteristics of soft soil deep foundation pit partitioned excavation

In this study, the deep foundation pit project of No.4 Wangjiang New City of Hangzhou New World is taken as a case study, and the zonal excavation process of the foundation pit is comprehensively monitored. Through the in-depth analysis of the monitoring data of the diaphragm wall deformation, soil inclinometer measurements, wall top settlement, and ground settlement outside the pit, and combined with the numerical model of the foundation pit zonal excavation established by PLAXIS 3D, we compare the numerical simulation results with the actual monitoring data to validate the accuracy of the model and to supplement the insufficiency of the monitoring data. The results show that the deformation of the diaphragm wall during the excavation of the foundation pit presents a typical parabolic variation pattern, and a push-back displacement toward the pit occurs during the post-excavation construction stage. The deformation characteristics of the soil outside the pit are similar to those of the diaphragm wall, but its deformation magnitude is relatively small. With the progress of foundation pit excavation, the ground settlement outside the pit increases gradually, and its displacement curve deviates from the traditional parabolic variation pattern due to the influence of environmental factors. In addition, the wall top settlement shows a clear trend of “first heave and then settle” during the foundation pit excavation and the construction of the main structure inside the pit.