Re-analysis of the deformation of rock-based scour protections around monopiles exposed to waves and current

Publicly available data on the deformation of scour protections around monopiles were collected, reviewed, and re-analysed. Studies published over the past two decades were found to be comparable and overall consistent. The re-analysed dataset, based entirely on physical model tests, was examined using both qualitative and quantitative approaches. Qualitative analysis shows that deformation patterns can be uniquely classified by the Shields number and wave–current ratio, while the influence of the relatively low Keulegan–Carpenter (KC) numbers covered by the data is negligible. Quantitative results confirm similar trends in deformation magnitude. Analysis of deformation time scales reveals a dependency on wave–current ratio comparable to live-bed scour, though with longer time scales. Based on these findings, a preliminary design methodology for optimised armour rock protection is proposed, alongside a discussion of data limitations and associated risks.