Fluid-solid coupling large deformation failure analysis of bucket foundations in saturated clay

The suction bucket foundation, utilized as the structural foundation for offshore wind turbines, generates pore pressure accumulation and reduces effective stress and eventually leads to failure through fluid–solid coupling during installation. To accurately predict changes in the load-bearing capacity of the suction bucket foundation during installation, a numerical simulation method for large deformation in fluid–structure coupling of saturated clay is proposed. The approach utilizes ABAQUS with its secondary development module, integrating the RTISS calculation method, the modified Cambridge soil model, and Biot consolidation theory. The accuracy of the RITSS large deformation finite element method for analyzing the penetration problems in saturated clay was validated through simulations of the cone penetration test (CPT). A numerical model was developed to analyze fluid–solid coupling in the suction bucket foundation during penetration and to assess the bearing capacity stability throughout installation. The results indicate that the normalized penetration resistance of a bucket foundation in Malaysian kaolin clay is 6.53. Within the initial 10 days, excess pore water pressure at the base of the bucket foundation decreased by 28 %, with the coefficient (Tc50) for 50 % maximum pore pressure dissipation time measured at 0.022. The proposed numerical simulation method for pore pressure dissipation was validated, providing valuable insights into addressing fluid–solid coupling in large deformation simulations of saturated cohesive soil.