Inferred Winkler model for uplift response of suction caisson in undrained clays

Suction caisson jackets are promising foundation solutions for offshore wind turbines (OWTs) in deep water. The resistance of such a foundation against overturning actions depends on the uplift response of individual caisson. Winkler models (i.e., foundation displacement versus soil reaction relationships) have been shown powerful and efficient in modeling general soil-foundation interactions, whereas those targeting suction caisson subjected to tensile loading are relatively underdeveloped. The goal of this study was to construct a soil reaction model capable of accounting for site-specific soil stress-strain relations and project-specific foundation geometries. This objective is pursued via the concept of "inferred Winkler model" and by constructing soil reaction curves based on the outcomes of rigorous numerical modeling. First, finite element analyses (FEAs), in combination with a well-established hyperbolic soil model, are utilized to evaluate the soil reaction responses associated with vertically loaded caisson in undrained clays. The FEA then establishes the interrelationships between the key characteristics of soil reaction behavior, soil stress-strain relations, and foundation geometries, leading to an inferred Winkler model capable of directly utilizing soil model parameters. Lastly, the proposed soil reaction model is assessed against centrifuge test results and shown capable of reasonably representing test observations and delivering solutions comparable to FEA but at a much lower computational cost.