Abstract
Bottom-fixed offshore wind turbines are generally built on continental-shelf sections that are morphodynamically active due to their shallow depths and severe wave and current conditions. Such sites are commonly protected against scour to prevent the loss of structural stability. Scour protection can be designed using static or dynamic solutions. Designing dynamic protection requires experimental validation, especially for singular or unconventional structures. This article presents an experimental method for the laboratory analysis of scour protection for jacket foundations placed at morphodynamically active sites. The test campaign was conducted within the project East Anglia ONE (UK) as part of the asset owner studies and aimed to evaluate operation and maintenance (O&M) aspects, independent of the contractor’s original design assessments. The physical experiments explored morphodynamic changes on the sea bottom and their importance to scour protection, as well as the importance of the history of the wave loads to the deformation of the rock scour protection. This was explored by repeating different cumulative tests, including a succession of randomly ordered sea states (Return Period (RP) 1-10-20-50 years). The experimental results show that the deformation of the rock sour protection was the greatest when the most energetic sea states occurred at the beginning of the experimental test campaign. The maximum deformation was at 5D50 when the first test was also the most energetic, while it was at 3D50 when not included as the first test, yielding a 40% reduction in the scour protection deformation.
Highlights
At the end of 2019, the total European offshore wind power capacity was 22,072 MW, which is equivalent to 5047 turbines, according to [1]
The results were divided into two sections: First, the results of the sand wave evolution and its interaction with the rock scour protection are shown
This paper described an experimental approach to this problem that focused on the analysis of two aspects: the importance of elements such as sand waves in the behavior of scour protection, and the importance of the hydrodynamic history of environmental loads on scour
Summary
At the end of 2019, the total European offshore wind power capacity was 22,072 MW, which is equivalent to 5047 turbines, according to [1]. For structures with more complex geometries, such as gravity base foundations, jackets, or other designs, there is a lack of semi-empirical formulations for validating rock scour protection (dynamically or statically stable). There are no open publications that show the behavior of rock scour protection for jacket foundations located in sites with active morphodynamic environments (like the research shown in [23] for monopiles). The present article aims to deepen the knowledge on the medium to long-term dynamics of rock scour protection for jackets located in sites with active morphodynamic environments For this purpose, an experimental test campaign was performed at a 1:30 scale in order to evaluate the scour protection behavior of the jackets of East Anglia One (UK, ScottishPower, Iberdrola Group).
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