Bearing behavior of suction bucket foundations under tensile loading in non-cohesive soils

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Suction Buckets are a promising alternative to driven piles as foundation elements for offshore wind energy converters. For multipod foundations with three or four buckets the cyclic tension load is design-driving in the dimensioning of the buckets. However, significant knowledge gaps exist regarding the prediction of the tensile resistance. The specific problem herein is the estimation of the suction pressure occurring inside the bucket during loading, which is dependent on loading rate and duration, soil permeability and bucket geometry. At the time being, no applicable design concept exists which allows consideration of this suction pressure. However, neglecting the suction considerably reduces the economic and ecologic advantages of the bucket foundation.The applicant developed a numerical model which enables the determination of the tensile bearing behavior dependent on the mentioned influence parameters. However, the corresponding literature review showed considerable deficiencies in the understanding of the basic phenomena and in number and quality of the experimental investigations carried out so far. Therefore, model tests shall be carried out in the research project, which shall form a basis for a sufficient validation of further numerical simulations. Tests with constant loading rates, with rapidly increased and then constant load and cyclic loading tests are foreseen. Detailed parametric studies for different system and loading conditions shall be carried out with the validated numerical models. Based on the results, a design method for the estimation of the tensile resistance of a suction bucket under arbitrary soil and loading conditions shall be developed.