Uplift capacity of suction anchor groups for floating offshore wind turbines: Loading-angle and mooring-position effects

To address the limitations of single suction anchors in deep-water environments, this study investigates mooring-loaded suction anchor groups as an innovative anchoring solution for high-power Floating Offshore Wind Turbines (FOWTs). The uplift capacity and failure mechanisms of suction anchor groups were systematically evaluated via 1 g physical model tests and 3D Finite Element Method (FEM) simulations. Results reveal a fundamental transition in the pullout resistance-displacement curves: unlike the strain-hardening behavior of single anchors, anchor groups exhibit pronounced strain-softening characteristics owing to the increased overall stiffness of the soil-anchor system. The bearing performance of the anchor group is further influenced by loading angle, while the effect of mooring-point position depends on the loading condition. With increasing loading angle, the dominant resistance mechanism gradually shifts from passive soil resistance to skirt friction-controlled vertical uplift. The sensitivity of bearing capacity to mooring position is governed by the dominant failure mechanism and decreases with increasing loading angle. At larger loading angles, the influence of mooring position becomes limited due to the transition toward a vertical uplift mode. These findings are expected to provide valuable guidance for optimizing the design of suction anchor group mooring systems under complex loading conditions.