Investigations on scour development around a gravity foundation for offshore wind turbines

Abstract

Due to insufficient insights about the scour development around the STRABAG gravity foundation, the Franzius-Institute conducted small- and large-scale physical model tests in wave flumes on a scale of 1:50 and 1:17 in order to investigate the wave-induced scouring phenomena around the foundation and to design a scour protection system. The tests on scour development without a scour protection system show that the main areas which are vulnerable to scour are the contact areas of the foundation. Furthermore, the experiments show that a scour protection system is necessary for the given and investigated wave boundary conditions; the performance of the selected protection system using geotextile sand containers is verified. Additional numerical simulations indicate an amplification of the resulting flow around the foundation under combined loads (waves and current), but without significant change of the flow pattern.