Experimental and Numerical Investigation of the Performance of Suction Buckets Subjected to Extreme Cyclic Tensile Loading in Sand

Abstract

Suction bucket jackets offer a promising foundation solution for offshore wind turbines. However, extreme cyclic tensile loading can be a significant design challenge, particularly with respect to the potential for accumulated upward displacement, which can lead to permanent tilting of the foundation. This paper presents findings from 1 g model tests on a suction bucket in sand under various cyclic tensile loading configurations, focusing on the evolution of displacement, stiffness, and excess pore pressure. The results show that lower frequencies, higher peak loads, and higher mean loads lead to greater upward displacement accumulation. Notably, significant and progressive bucket uplift was observed even when the applied peak load was within the drained tensile capacity. A new concept of yield tensile capacity was proposed, providing a reasonable interpretation and accurate evaluation of peak load effects on displacement accumulation. Postcyclic monotonic tensile loading tests revealed an increase in both drained tensile capacity and stiffness of the bucket, attributed to local densification of the sand around the bucket. Moreover, calibrated finite-element analyses were performed to supplement the model test results. These findings provide valuable insights for designing windward bucket foundations under jacket structures.