New methods for the scour protection around the pile foundation based on oyster reef cover

Offshore wind turbines usually suffer from severe local scour and environmental challenges. Two novel eco-friendly technologies—oyster reef cover (ORC) and grouting overlaying oyster reef cover (GORC) were proposed as scour countermeasures. In this paper, a series of current scour tests were carried out under the protection of ORC, GORC, riprap, and sacrificial piles. The experimental observations indicated that ORC and GORC could significantly reduce the scour depth. The protection efficiency of ORC and GORC significantly surpasses that of riprap and sacrificial piles. The protection efficiency of ORC is proportional to its extent. When thickness increases, the protection efficiency increases and then decreases. An equation to calculate the protection efficiency of ORC was proposed. The optimal protection parameters were given as ${W_{OR}}_C/D=7$ and ${t_{OR}}_C/h=0.187$, which can reduce 98.8 % of the scour depth. Mechanistically, the ORC weakens the underflow and horseshoe vortex, while the slurry enhances the seabed scour resistance. Consequently, the GORC can reduce 99.8 % of the scour depth. The GORC showed superior stability compared to ORC, surpassing riprap. The ecological value and economic advantages of ORC and GORC were discussed. The present work provides a reference for the design of scour protection systems that integrate wind power development, ecological restoration, and marine pasture management.