Abstract: To investigate the lateral cyclic loading response of large-diameter monopiles in soft clay, a series of centrifugal model tests of large-diameter monopiles in soft clay were conducted under different cyclic loading patterns (unidirectional and bidirectional). The deformation characteristics, stiffness degradation, pile bending moment of large-diameter monopiles, cyclic p-y curves and variations in excess pore water pressure around the pile were systematically analyzed. The test results indicate that the load-displacement curves of the monopile exhibit pronounced nonlinear retardation energy consumption and displacement accumulation characteristics. Compared to one-way cycle loading, two-way cycle loading causes a significant cumulative displacement of the pile top, which is influenced by both the number of cycles and the loading amplitude. The cumulative displacement of the pile top consists of recoverable elastic deformation and irrecoverable plastic deformation, with the plastic component being dependent on the number of cycles and the applied stress level. The two-way cycle loading causes a more significant degradation of pile-top stiffness, resulting in a greater bending effect along the pile shaft. The accumulation of excess pore-water pressure around the pile is also related to the number of loading cycles and the loading amplitude and is notably more pronounced under two-way loading conditions.

Key words: offshore wind turbines, pile foundation, cyclic loading, soft clay, centrifuge test