Geotechnical Analysis and Modeling for Offshore Wind Turbine Monopiles in Gulf of Bothnia Soil Conditions

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Offshore wind energy is currently experiencing a period of rapid growth both globally and in Finland. Over the past decade, wind turbines have been installed in the sea areas of Northern Finland, and the size of wind farms has also increased. There are numerous methods for installing wind turbines, but the most common offshore wind farm foundation in Europe is the monopile. This paper analyses the modeling of sandy soil behavior under complex cyclic wind and ice loads. The advanced soil models SANISAND-MS and Hardening soil small (HSsmall) are used. The loads were simulated using the ice load portal developed by the Technical Research Centre of Finland (VTT). Modeling was carried out using Plaxis 3D with a 15MW virtual wind turbine with a 10-meter diameter monopile foundation published by the National Renewable Energy Laboratory (NREL). The study examines the soil deformation induced by both cyclic and static loading, as well as the displacement of the monopile foundation in various loading conditions. The results showed that under cyclic loading, the displacements increased after each load cycle, creating permanent soil deformations. For low design loads, the magnitudes of displacement predicted by SANISAND-MS and HSsmall were found to be of the same magnitude. However, differences between the material models were observed as the load magnitudes increased. The HSsmall model showed larger displacements in dynamic analyses compared to similar static loading scenarios. The SANISAND-MS model encountered numerical problems and failed to simulate the monopile foundation under storm loading conditions.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

9 - Monopile design to cyclic loads: quasi-static, dynamic and seismic loads