Determination of p-y Curves for Bucket Foundations in Silt and Sand Using Finite Element Modelling

Design of offshore wind turbine foundations are today based on analytical formulas, which describes the link between a displacement, y, and the associated soil pressure, p. The formulas are empirically developed on slender piles with a slenderness ratio L=D > 30, but foundations of today are less slender than the tested piles. The suction bucket has a slenderness ratio of 0.5-1, thus its response is a rigid movement, where slender piles undergoes a flexible movement. Due to the importance of precise estimations, p-y formulations for suction buckets in drained and undrained silt are sought developed with use of finite element. In general the developed p-y formulations for the drained and undrained silt are fairly precise. Furthermore, the same method and basic formulation of the drained silt is applied to data of the drained sand from Østergaard et al. [2015]. The developed formulation herefore shows to be more versatile and precise than the formulation suggested by Østergaard et al. [2015]. The developed p-y formulations are functions of the effective vertical in-situ stress, soil stiffness, diameter of the bucket and the internal friction angle/the undrained shear strength.