Model tests on horizontal load-bearing and deformation resistance capacities of pile-bucket foundation in soft seabed soil

Large-diameter pile-bucket foundations are a new type of foundation used for offshore wind turbines. In this study, model tests were performed on pile-bucket foundations to investigate their load-bearing and deformation resistance capacities. The strains of the pile and bucket and the horizontal displacements at the loading point were measured using strain gauges and displacement transducers, respectively. The variations in moments of the pile and bucket with depth were calculated and fitted into polynomial functions of sixth to eighth orders. Based on the moment polynomials, the distributions of the horizontal displacements and soil reaction of the pile and bucket were determined according to the beam bending theory. Improvements in the load-bearing and deformation resistance capacities were quantitatively determined by comparing the test results for the pile-bucket foundation with those of the monopile foundation. The initial stiffness and ultimate horizontal bearing capacity of the pile-bucket foundation were 50% and 20%, respectively, higher than those of the monopile foundation. For sections within the bearing depth of the bucket, the ultimate soil reaction force of the pile-bucket foundation was 20 times that of the monopile foundation. However, a 10%–20% improvement in the ultimate soil reaction was observed for deeper sections.