A further study on the scour around the monopile foundation of offshore wind turbines

Foundation scour has long been a concern in the offshore wind industry as it poses a great threat to the safety of offshore wind turbines (OWTs). However, the current understanding of this issue is still insufficient. This is because many offshore wind farm factors and their coupling effect on scour have not been fully investigated. Therefore, two phases of experimental studies are conducted in this paper to investigate how monopile vibration, water flow, and intermittent operation of OWTs work together to affect the scour around the monopile foundation. The research results have shown that in the absence of water flow, monopile vibration can also create 'scour pits' while causing soil densification. The coupling of a large-amplitude monopile vibration and the water flow will exacerbate the scour, while the coupling of a small-amplitude monopile vibration and the water flow will retard the scour. The vibration amplitude has a greater influence on the scour than the vibration frequency. In addition, vibration sequence was found to have a significant effect on the scour, but despite the sequence, repeated application and removal of monopile vibration, which represents the intermittent operation of OWTs, can lead to severe foundation scour.