Model test investigation of offshore wind power monopile scour protection measures based on cemented riprap underwater

Cemented riprap underwater technology uses good antidispersion performance and high-fluidity characteristics of underwater self-protecting concrete or mortar to fill the gaps between underwater blocks to form cement with a definite structural strength. This paper covers the first instance of cemented riprap underwater technology being applied to the field of scour protection for offshore wind power monopile foundations. Based on the cemented riprap underwater technology, this paper proposes anti-scouring measures for offshore wind power monopile rock-filled concrete, and uses a 1:13 large-scale wave current physical model test to study the anti-scouring performance of underwater structure around piles. Tests have shown that the plum-shaped pouring method can form a complete cemented riprap underwater protective structure. This protective structure can maintain good integrity and stability. Under extreme wave and current conditions with a return period of 50 and 100 years, the maximum scour depths of the sand around the monopile are 4.00 and 6.24 m, and the scour pit widths are 6.50 and 13.75 m, respectively. After the cemented riprap underwater protective structure, the maximum scour depths of the soil around the pile are 2.96 and 4.42 m, and the scour pit widths are 2.65 and 4.55 m, respectively. The above results provide new ideas for the protection measures and scour restoration of offshore wind power monopile foundations.