Four composite support structures are proposed for the 2,000-ton-class second-line ship lock project at Xinglong Junction.Based on the soil hardening model,a finite element model of the deep foundation pit composite support system is established to analyze and compare the pile bending moment,shear force,and overall displacement of different composite support systems.The comprehensive evaluation of each supporting structure is conducted by analyzing factors such as construction organization,resource input,construction efficiency,and cost.The results indicate that the cellular diaphragm wall exhibits the highest structural stiffness,but it is difficult to construct with the highest cost.The double-row steel sheet pile combined with steel pipe piles offers superior integrity and continuity of the support structure,along with convenient construction organization and equipment mobilization,while it faces the challenge of driving large-diameter steel pipe piles in deep and thick gravel layers.The double-row cast-in-place pile combined with a buttress retaining wall optimizes the diaphragm wall to the cast-in-place pile,yielding distinct cost advantages.The double-row cast-in-place pile combined with steel sheet pile adopt a separate design for water cutoff and support,which achieves the best comprehensive evaluation.Field application of this support technique reveals that during the flood season,the maximum deformation of steel sheet piles is 198 mm,the maximum displacement of cast-in-place pile tops is 125 mm,the maximum axial force of inclined support pipe is 172 kN,and the maximum bending moment of front-row cast-in-place piles is 675 kN·m,which verifies the structural safety and stability.