Abstract: Tetrapod bucket foundations are formed by four suction buckets into a square shape and connected by superstructure into a whole to provide better resistances against severe marine environmental loads than single bucket foundation. Tetrapod bucket foundations can serve as foundations for offshore platforms or wind turbines, and show a broad application prospect. To investigate the bearing capacities and failure mode for single and tetrapod bucket foundations, and optimizing the design of tetrapod bucket foundations, this paper established a large number of 3D finite element models of tetrapod bucket foundations in soft soil and systematically investigated the effects of bucket separation distance on uniaxial capacities and corresponding failure modes with different foundation embedment depths and soil strength heterogeneities. Results indicate that vertical capacity factors are almost independent on the bucket separation distance while horizontal capacity factors are evidently dependent on separation distance, and moment capacity factors are especially affected by separation distance. All uniaxial capacity factors of tetrapod bucket foundations increase as embedment depth increases, but decrease as soil heterogeneity index increases under the same bucket separation distance ratio. By analyzing uniaxial capacities, corresponding failure mechanisms and group effect factors of tetrapod bucket foundations, optimal bucket separation distance of tetrapod bucket foundations was defined, which can provide reference for optimizing the design of bucket separation distance of tetrapod bucket foundations.

Key words: tetrapod bucket foundations, optimal separation distance, bearing capacity, failure mechanism, soft soil