Buckling characteristics of bucket foundations under suction installation in spatially variable clay

Abstract

The suction bucket, also termed the suction caisson, is a cost-effective offshore foundation widely used in wind farms worldwide. However, there is a risk of buckling in thin-walled skirts during suction installation, with several incidents highlighting the need for improved buckling design. Previous studies focused on idealized boundaries and homogeneous soils, neglecting soil spatial variability. This study uses the random finite element method to investigate the buckling behaviour during installation in spatially variable soils while considering real geometric and eigenmode imperfections. The results show that soil variability reduces eigenvalues and alters eigenmode symmetry in linear buckling analysis. In nonlinear buckling, the failure mode is closely linked to the relative strength distribution of the soil, and the buckling pressure under real imperfections is significantly greater than that under modal imperfections. As the penetration depth and imperfection amplitude increase, the buckling transition from peak collapse to failure is controlled by the maximum allowable rotation. The design based on the first random eigenmode is more conservative than the deterministic approach is. Finally, safety factors corresponding to a 1% failure probability are provided, considering the penetration depth and fabrication tolerance class. This study offers valuable insights for the buckling design of suction caissons.