Time Scale of the Scour Process Around Monopile: A Case Study at Southwest Offshore Wind Farm, South Korea

The scouring issue requires to be considered carefully regarding offshore foundation design and management. Several experiments and field measurements indicated that the estimated maximum scour depth using the existed methods is inconsistent with the actual values for offshore wind farms and the time scale of the scour development in practical calls for further discussion. In this study, an overview of the scour mechanism around circular piles is introduced. A set of equations for the prediction of scour depth in different conditions is summarized. The scour development at Southwest Offshore Wind Farm in South Korea is reported. Based on the measured metocean condition, the effect of tidal current conditions, in relation to the time scale of the scour process around two monopile foundations with different diameters is analyzed. The effect of waves in a scouring environment is compared and discussed. It is found that scouring around a monopile develops rapidly within a relative shorter time, and then increases gradually to the equilibrium scour depth. The value of the equilibrium scour depth around a monopile varies greatly with the current velocity and monopile diameter. The effect of wave action on the scour depth around monopiles behaves differently on different sizes of monopiles. The equilibrium depths under the current alone condition and combined waves and current conditions are nearly the same.