Numerical study of cyclic response of suction bucket interfaces using a three-dimensional critical state model

Although many numerical studies have examined the response of suction buckets under cyclic compressive loading, most have concentrated on the cyclic behavior of the seabed soil. In contrast, the cyclic behavior of the interface between the suction bucket and the seabed has often been overlooked. To fill this gap, this study conducts a numerical analysis of the dynamic response of suction buckets embedded in sand seabed under cyclic loading. A state-dependent two-surface plasticity model based on critical state theory was integrated into a finite element framework. To address the limitations of conventional thin-layer and zero-thickness elements, a geometry-independent thin-layer element is developed, which avoids explicit thickness modeling while capturing volumetric and cyclic interface behavior. The seabed was modeled using a cyclic elastoplastic soil model. The numerical approach was validated against laboratory element and model tests. The cyclic response of suction buckets under compressive loading was examined considering interface roughness and seabed relative density. Lid resistance was found to dominate the total resistance, with increased roughness reducing settlement, while loose seabeds led to much larger settlements than dense ones. The perfectly elastoplastic interface model underestimated settlement and weakened the influence of roughness on resistance evolution.