Centrifuge modelling of suction anchors under multidirectional loading for shared mooring applications

Shared anchors for floating offshore wind turbines (FOWTs) offer potential cost savings, but their geotechnical performance under complex multidirectional mooring loads in soft clay requires better understanding. To address this, centrifuge modelling was conducted at 75 g on model suction anchors in normally consolidated kaolin clay. The experiments simulated several loading scenarios, including monotonic pull-out and multidirectional loading patterns representing shared anchor configurations (three lines at 45° inclination to the horizontal plane, spaced by 120° azimuthally). Three load tests were performed: a monotonic reference test and two multidirectional tests involving alternating and simultaneous line loading. Measurements included the anchor load–displacement response and excess pore pressures with complementary data from digital image correlation. The baseline monotonic test yielded an ultimate capacity of approximately 4 MN. Alternating line loading induced progressive downward displacements, while simultaneous two-line loading produced a trend of upward movement. Simultaneous loading also led to greater horizontal displacements, reflecting increased mobilisation of soil shear strength under compound loading paths. Post-multidirectional monotonic tests revealed reductions in anchor capacity between 10% and 38%, depending on the load path history and inclination. This work delivers benchmark data clarifying suction anchor behaviour under multidirectional loads to validate numerical models and optimise shared anchor designs for FOWTs.