Analysis solution of the lateral load response of offshore monopile foundations under asymmetric scour

Abstract Because of the directivity of the waves and flow, the scour hole presents an irregular shape, and the scour hole dimensions are different around the pile. In this paper, an asymmetric scour is defined in the calculation of the laterally loaded offshore monopile foundations considering scour. Then, the effective overburden stress and the effective strength of the remaining soil after scour are determined based on the solution of Boussinesq's point load due to the unloading of the scour. An analysis p-y method is developed under the condition of the asymmetric scour based on the p-y curve proposed by Matlock for soft clay and the p-y curve proposed by Reese for sand, respectively. The effect of the scour depth, scour width and scour slope angle on both sides of the piles on the lateral loaded piles are determined in both soft clay and sand. Finally, according to the results of the parameter studies, a simplified method applicable to small-diameter flexible piles is developed based on the pile head deflection before scour, scour depth, loading height and pile diameter to predict the lateral loaded pile head deflection after scour in soft clay and sand, respectively.