Schematic design and performance of retaining structure for waterfront excavation

In combination with the schematic design of a large-scale waterfront deep excavation for passenger station adjacent to the front wharf on piles, a kind of composite steel sheet pile retaining structure scheme for the foundation excavation is proposed to satisfy the waterfront construction condition of retaining structure and to minimize the design alteration of the front wharf on piles. The two-dimensional finite element numerical models are established with Plaxis to study the deformation and mechanical performance of the two feasible waterfront retaining structure schemes, including diaphragm walls and composite steel sheet piles. The calculated results show that the composite steel sheet piles can be constructed in parallel with the front wharf on piles in water so as to avoid massive backfill and subsequent excavation. This leads to the decrease of earth pressure loading on the retaining structure during inside excavating and strutting, which brings positive effects on deformation control and overall stability of the excavation. The maximum lateral deflection of the composite steel sheet piles is only one third of the diaphragm walls when the pit is excavated to the bottom, which means the steel sheet piles with two rows and the cast-in-place concrete can exert the stiffness of the composite load-carrying structure effectively. The proposed composite steel sheet pile retaining structure scheme can provide a useful reference for the design and construction of similar waterfront excavation projects.