Numerical investigations on the behaviour of suction bucket foundations under cyclic axial compressive loads

Suction buckets are an alternative foundation type for offshore structures. Due to their widely noise emission-free installation, they can be used instead of usual offshore foundations with driven piles. Cyclic loads induced by wind, water waves and currents play a special role for the design of suction bucket foundations. These loads can lead to an accumulation of permanent soil deformations and excess pore water pressures in water saturated soils. This has to be considered in ultimate limit state and serviceability design. In this paper the interaction behavior of soil-bucket-systems subjected to cyclic axial compressive loads is analyzed using a finite element model. A fully coupled two-phase model and a hypoplastic constitutive model for the water saturated soil are used in the numerical analyses. Special attention will be dedicated to interactions between the structure, the water-saturated soil and the pore water. The influence and relevance of some of the main system and loading parameters that affect the pore water pressure development in water-saturated soil are studied on the basis of parametric studies. In there the cyclic loading number, the frequency, the embedded length and the diameter of top plate of the bucket are varied. Based on these investigations the importance and relevance of the consideration of cyclic accumulation effects with soil-bucket-systems is demonstrated and the key findings are presented.