Bearing performance of suction anchor groups in marine clay: Pull position and aspect ratio effects

With the expansion of Floating Offshore Wind Turbines (FOWTs) into deeper waters, conventional individual suction anchors often struggle to meet ultra-high mooring load requirements. This study proposes a triangular suction anchor group connected by a top rigid frame to mitigate the insufficient bearing capacity of single suction anchors. Finite element method (FEM) was performed to investigate its pull-out bearing behavior and failure mechanism in marine soft clay, and the numerical method was validated against physical model tests. The results demonstrate that the suction anchor group markedly improves the peak pull-out force, initial stiffness and overall stability compared to a single anchor. The effects of the anchor aspect ratio and pull position (pad-eye position and loading direction) were systematically investigated. The pad-eye position and loading direction govern the failure mode of the group foundation. Increasing the anchor aspect ratio from L/D = 2 to 3 effectively suppresses lateral rotation, drives the plastic zone deeper into the soil, and increases the peak pull-out force to approximately 1.64 times that at L/D = 2. Combined analysis of the efficiency of the group anchor system and plastic zone further reveals the underlying mechanism behind the substantial bearing capacity enhancement of the anchor group system.