Abstract: Considering the complexity and cost of field testing, this study established a three-dimensional finite element model based on an actual offshore wind power project. The model was used to simulate the interaction among cement-soil mixing piles, the steel pipe pile, and the surrounding soil. It was further employed to investigate the effects of key reinforcement parameters on the lateral bearing behaviour of the steel pipe pile. The results indicate that increasing the reinforcement width and depth of cement-soil mixing piles enhances the lateral bearing capacity of the single pile. When the reinforcement width and depth are 2D and 3D, respectively, the reinforcement efficiency is relatively high. Furthermore, an appropriate layout improves both the structural performance and the reinforcement efficiency, increasing the lateral ultimate bearing capacity by approximately 150% compared with the unreinforced condition. Comparative analyses of pile displacement, lateral load-mudline rotation, bending moment, and pile-side soil resistance under different reinforcement schemes show that the pile-head horizontal displacement is reduced by 43.93%~56.68%, the maximum pile bending moment decreases by 7.32%~24.37%, and the pile-side soil resistance within the reinforced zone increases significantly

Key words: finite element analysis, large diameter steel pipe pile, cement-soil mixing pile, horizontal bearing characteristics, engineering design optimization