Axial Load-Transfer Curves for Suction Bucket Foundations in Sand

Multi-footed structures resting on suction buckets (suction caisons) comprise a promising foundation solution for next-generation 10 MW+ offshore wind turbines located in transitional water depths. For such systems, predicting the axial behavior of buckets is a critical design aspect. Load-transfer or t–z curves have been employed for decades as an efficient tool in pile design, however applying existing formulations to suction buckets bears uncertainty. This paper introduces a novel family of static t–z curves (Winkler springs) for suction buckets installed in typical marine sand. The study is based on 50 finite-element models that involve various foundation dimensions and soil properties, as well as drained uplift and compression. The non-linear springs’ properties are therefore linked to suction bucket diameter, friction angle and vertical overburden pressure. Lastly, good agreement is found between the current results and the ones from other numerical studies. Since the proposed t–z curves require only three basic parameters, they may be conveniently implemented in preliminary stages of foundation design.