The Yangshan deepwater port is the only container port built in the islands off the mainland of China. Batter piles with a sheet-pile supported platform bulkhead structure was firstly used as a new shore-connecting structure to connect the front main wharf structure and the back land. Large-diameter sand columns were also used to reinforce the soft foundation of the shore-connecting structure in the deep water of the open sea. 3D nonlinear FEM model based on real geological conditions was built to optimize the large-diameter sand columns reinforcing scheme and investigate shore-connecting structure's mechanical properties under different construction conditions. The replacement ratio of 30%, the bottom elevation of the fourth soil layer, and the soft soil just below and directly adjacent to the shore-connecting structure were determined as optimal replacement ratio, reinforcing depths and reinforcing area of the large-diameter sand columns reinforcement by assessing the force and deformation of shore-connecting structure. By numerical computing, the maximum displacement of supported platform was 11.03 cm which was close to the measured value; and the piles' maximum stress, Downloaded by [Selcuk Universitesi] at 01:15 04 February 2015 2 displacement and moments were all smaller than the design strength. These indicated that the shore-connecting structure could remain stable by optimal sand columns reinforcing scheme.