Inspection of a high-cycle accumulation model for sand based on recalculations of a full-scale test on a gravity base foundation for offshore wind turbines

Abstract

Offshore wind turbines (OWT) are generally founded on piles or gravity base foundations. Up to now, there is a lack of validated and standardized analysis procedures for such foundations, especially for the serviceability limit state, i.e. for the prediction of accumulated deformations. In order to gain experience on the behaviour of a OWT gravity base foundation under typical offshore loading conditions, a full-scale test has been performed near the shore of the North Sea. The test foundation was subjected to about 1.5 million load cycles simulating several storm events. The foundation and the sandy subsoil have been extensively instrumented so that a large amount of measured data on the cyclic soil-structure interaction were collected. Meanwhile, a numerical procedure for the proof of the serviceability for OWT foundations was developed. The procedure is based on finite element (FE) calculations in combination with a high-cycle accumulation (HCA) model. The application of the HCA model in simulations of the full-scale test is described in this contribution. The essential simplification of the subsoil and the determination of the input parameters for the FE simulations are shown. The settlements, pore water pressures and soil pressures predicted by the HCA model are compared to the measurements.