Modelling pullout of suction buckets under varying rates

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Suction bucket jacket is one of the major foundation types being adopted for supporting offshore wind turbines. With combined effects of increasing water depths and environmental loads and more optimised bucket size, the tensile capacity of the bucket may become a critical design issue. In this study, a parametric study has been carried out through numerical modelling to investigate the uplift performance of a suction bucket in sand considering a range of pullout rates, thus drainage conditions. In order to capture the key constitutive behaviour of the sand relevant to the problem of interest, an advanced bounding surface constitutive model, termed SANISAND-F, has been employed. This model can not only replicate the shear induced dilation of dense sands realistically, but also account for the effect of in-situ fabric effects. Additionally, coupled fluid-mechanical interaction analysis is also necessary in order to model partial drainage conditions. In this paper, the performance of the numerical model was first validated against centrifuge test results. Then a series analyses were performed by vertically pulling out the bucket at a range of velocities to cover the entire drainage regime from undrained, partially drained to drained conditions. The results of the analyses show significant effect of the drainage conditions on the uplift performance of the bucket and provide valuable insights into the underlying mechanisms which explains why the pullout behaviour varies under different drainage conditions. Associated interaction between fabric orientation and loading direction in different drainage conditions has also been discussed.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

11 - Suction installed foundations and anchors