Abstract: Herein, to investigate the characteristics of dewatering, excavationinduced deformation, and groundwater variation in an ultrawide pitinpit in the Binhai avenue renovation project in Shenzhen, China, deflection of retaining structures, settlement of surfaces and surrounding structures, and correlation between groundwater and tidal water are analyzed using a field monitoring method. Moreover, a threedimensional fluidsolid coupling model is established considering tidal water replenishment using the ABAQUS finite element software to explore the development characteristics of underground diaphragm wall deflections during dewatering and excavation processes. The model validates the control effect of the staged dewatering control method and steel bracing change scheme on wall deformation. The following conclusions are drawn: (1) During the excavation process, the maximum wall deflection is 29.5 mm and the north and south wall tops move outward. Further, the maximum surface settlement is 29.4 mm, and the vertical displacements of columns and surrounding structures are <6.5 mm. (2) Tidal water replenishment and rainfall lead to a water level drop of approximately 〖WTBZ〗-〖WT５《TNR》〗1.0 m in the north and 〖WTBZ〗-〖WT５《TNR》〗1.5 m in the south outside of the pit. (3) During the dewatering and excavation phases, the staged dewatering control method and steel bracing change scheme reduce the maximum wall deflection by ~29% and 21%, respectively.

Key words: pitinpit excavation, deformation characteristics, dewatering, field monitoring, finite element analysis