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For offshore wind turbines, monopile foundations with diameters of 4–6 m are often employed. The Winkler model approach, where the soil resistance is modelled as uncoupled springs with spring stiffness’ given by p-y curves, is traditionally employed for the design of monopiles. However, this method is developed for slender piles with diameters up to approximately 2.0 m. Hence, the method is not validated for piles with diameters of 4–6 m.

The aim of the paper is to extend the p-y curve method to large-diameter non-slender piles in sand by considering the effects of the pile diameter on the soil-pile interaction. Hence, a modified expression for the p-y curves for statically loaded piles in sand is proposed in which the initial slope of the p-y curves depends on the depth below the soil surface, the pile diameter and the internal angle of friction. The evaluation is based on three-dimensional numerical analyses by means …