Pore Pressure Under a Gravity Based Structure Under the Influence of Waves

Abstract

The total wave load on a gravity based foundation for offshore wind turbines is influenced by the pore pressure from beneath the structure. The pore pressure is induced by the wave-structure-seabed interaction. Often the uplift force is included in a simplified way in the design of the gravity based foundation. This leads typically to very conservative designs in order to accommodate the uncertainties in the procedure. The experiments shall lead to better prediction models based on for instance CFD model’s with the direct calculation of pressure variations in the seabed and any erosion protection layer. Herewith, it will be possible to get a direct assessment of wave loads on the foundation, also under the seabed level. The study includes experiments as well as numerical analyses. A good agreement between the experimental results and the numerical analyses was found. In the numerical analyses, it was possible to investigate the effect of air content in the pores, which turned out to have an effect on the distribution of the pore pressure.