Comparative investigation of torsional interactive behaviours between suction anchors and clayey ground by centrifugal tests

Shared suction anchors offer a cost-reduction solution for the floating wind farm deployment. However, compared with the conventional anchor, the torsional load on the shared anchor is intensified, the ignorance of which may trigger a cascading failure throughout the wind farm. In this context, torsional interactive behaviours between suction anchors and clayey ground were investigated by centrifugal tests here. A conventional anchor and a finned anchor equipped with three fins along the skirt were tested. Test results showed that the ultimate bearing capacity of the finned anchor was almost 10 times that of the conventional anchor. Failure boundary was along the soil-skirt interface for the conventional anchor. The boundary was extended further than the fin edge for the finned anchor, demonstrating that the surrounding soil was mobilised to enhance the skirt resistance. Correspondingly, the total torsional resistance for the finned anchor was found greater than the summation of resistances from earth pressure on fins and soil-skirt friction. With the increase in depth, the torsional resistance normalised by the undrained shear strength rose in the conventional anchor, but dropped in the finned anchor. Based on these experimental observations, an enhancing factor of skirt resistance and a torsional load transfer model were proposed. The model has been validated to effectively reproduce the evolutions of torsional load at different depths in the finned anchor. Furthermore, it is capable of predicting the torsional bearing capacities of finned anchors with different fin widths, including the conventional anchor and vane shear tester.