Gap formation around suction caisson in sand under lateral cyclic loading

Suction caissons are extensively utilized for offshore wind turbines, which experience lateral cyclic loadings from wind and waves during operation. A ring-shaped gap gradually develops around the suction caisson due to lateral cyclic loadings. This paper describes a series of half-model tests in sand with different relative densities using digital image method to investigate evolutions of gaps (Δ), two-dimensional void ratios (e) and moment capacities (M). The gaps and two-dimensional void ratios adjacent to caisson walls were calculated by image processing and a Δ and e-based empirical formula was put forward to predict the moment capacity. The results indicate that both the gaps and two-dimensional void ratios exhibit a strong correlation with the loading amplitude, whereas they display limited correlation with the loading frequency; the bearing capacity is determined by the combined effect of gap size and two-dimensional void ratios. The empirical formula describes the weakening of bearing capacity well. The findings of this study contribute to a deeper understanding of the behavior of suction caissons under lateral cyclic loadings and provide valuable insights for the design and optimization of offshore wind turbine foundations.