Effects of the Submerged Height of Mangrove-Inspired Skirt-Pile Group on Scour Mitigation around a Monopile Foundation

Inspired by the geometric characteristics of mangrove roots, we propose to use a group of skirt-piles around a monopile foundation as a scour mitigation measure. In this study, the effect of the submerged height of the skirt piles on the scour process was evaluated using laboratory flume experiments. Images of the scoured bed were processed based on the photogrammetric method, from which the three-dimensional topography maps were reconstructed and quantitative analyses were performed. The results demonstrate that there is an optimum height of the submerged skirt piles above the mudline which approximates the diameter of the monopile at which the scour depth reaches a minimum. Up to 80% reduction in the volume of scour hole was achieved by using the mangrove-inspired skirt piles at the optimal submerged height. It was found that although the height of the skirt pile affects the maximum scour depth, it has limited effects on the location of the sediment deposition. The presence of the skirt-piles was found to result in a steeper slope of the scour hole in front of the monopile. Furthermore, the slope also slightly changes at the position of skirt piles, which suggests that the sediments between the skirt piles were densified as a result of pile-sediment interaction.