Author(s): J. M. Harris
Linked Author(s):
Keywords: Offshore wind; Scour research; Field monitoring; Monopile foundations
Abstract: Over the last two decades offshore wind has developed rapidly from relatively small scale projects in shallow coastal waters such as Horns Rev 1 and Rødsand 1 with a capacity of 160 MW and 166 MW, respectively, to projects such as Hornsea 3 with a capacity of at least 2,400 MW, 120–140 km from the coast and in water depths typically in the range -35 to -45 m LAT. As part of these developments there are specific requirements for scour hazard assessment relating to the associated foundation structures and the cabling necessary for in-field transmission and power export. Notwithstanding the advances in understanding, areas of uncertainty remain which require further examination and challenges that require further research. Typically as scientists and engineers we use real-life scour problems to help formulate the questions for detailed laboratory or numerical experiments. It is less common to use the associated field information to address some of those questions and yet the available data can offer the chance of exploring scour at full-scale using real marine soils, albeit with all the inherent uncertainty associated with measurements obtained in the field. Given the large amount of field data collected over the last few decades associated with offshore wind developments what have we learned and how has this data changed our understanding and direction for scour related research, both with scour and scour mitigation processes? The evidence database on scour, applied in this study was created primarily from monitoring data collected at UK Offshore Wind Farms, and relates primarily to monopile foundations in different sediment and hydrodynamic environments. The results from analysis of this monitoring data are presented in the standard parameters of scour depth (S) non-dimensionalised with foundation diameter (D), and the water depth (h) also non-dimensionalised by foundation diameter (Figure 1). The data supports the view that scour is a progressive process where the seabed sediment is naturally mobile and there is an adequate thickness of that sediment for scouring to occur. Combining this data with the laboratory reference data set (Sheppard et al., 2011) then Figure 2 is obtained. The field data relates to tidal-induced flows whilst the laboratory data represents unidirectional flow conditions. Both data sets fit within the same population, albeit with some scatter.
Year: 2024