Design method of geotechnical capacity for tripod suction bucket foundations in clay

The tripod bucket foundation is a prevailing selection for the fixed offshore wind turbine. The reliable evaluation of its geotechnical stability under harsh marine environment loading is of increasing demand by offshore engineering. Previous publications concerning the tripod bucket foundation are more focused on the relative compact size, where the skirt length is less than the diameter of the bucket and the ratio of spacing to diameter is less than 3. To address the ever-increasing installed capacity of the wind turbine and thus requirement for larger size of foundation, this paper extends the previous numerical analyses on the tripod foundation by including large longer skirt lengths or larger spacings in the normally consolidated soil. The failure mechanism of the largescale tripod bucket foundation under both the uniaxial and combined loading are systematically examined numerically in undrained clay. The expressions for assessing the ultimate bearing capacity and the failure envelope are proposed, covering a wide range of skirt lengths and foundation spacings. The feasibility of these equations to apply to practical bucket-soil interface property and the soil strength heterogeneity are also demonstrated.