On the pile tension capacity of scoured tripod foundation supporting offshore wind turbines

The application of tripod foundations in offshore wind turbines means that the piles are subjected to obvious uplift loads, while a process of soil erosion around offshore foundations caused by waves and currents, i.e. scour, can result in a reduced foundation capacity in vertical direction. However, currently few efforts have been made to evaluate the scour behavior around the tripod foundation, and the literature available on the investigation of scour effect on the tension capacity of tripod pile is also scanty. This study is to present a simplified method for the analysis of pile tension capacity of scour-affected tripod foundation in sand, which can account properly for various dimensions of the local scour hole formed around the tripod piles as well as that of the local scour hole under the main column of the tripod foundation. Based on a field scour measurement at a tripod foundation in the Alpha Ventus test site, a series of parametric analyses are performed by using the present method on a tripod pile under a wide range of scour-hole dimensions of the tripod foundation. The effects of depth, width, slope angle of the scour hole around both the pile and the main column of the tripod foundation as well as that of pile slenderness on the tension capacity of the tripod pile are discussed.