Upper-bound solutions to anti-overturning bearing capacity of suction caisson for offshore wind turbine in clays under undrained condition

Suction caissons supporting offshore wind turbines are subjected to eccentric horizontal loadings, which may lead to the overturning failure. This paper presents a modified three-dimensional (3-D) failure mechanism to predict the anti-over-turning bearing capacity of suction caissons in clay under undrained condition. The modified failure mechanism is composed of a meniscus-conical wedge having meniscus shape at the mudline and a spherical failure in deeper soil. The meniscus-conical failure wedge predicts the deformation of the mudline better than the traditional ring-conical wedge, and the spherical failure keeps a kinematically admissible velocity field, ensuring the accuracy of the upper-bound theorem. Accordingly, the anti-overturning bearing capacity of suction caissons are deduced based on the work-energy balance equation, following by optimizations of two parameters to approach the critical failure mechanism that offers the minimum energy dissipation. In addition, the reliability of the presented upper-bound analyses are verified against the results from finite element limit analysis (FELA) as well as existing experimental and theoretical methods.