Influence on the lateral response of offshore pile foundations of an asymmetric heart-shaped scour hole

Abstract

The presence of local scour seriously jeopardizes the safe operation of offshore wind power systems, as local scour leads to the formation of scour holes, which will decrease the bearing capacity of the foundations of these structures. Due to the directionality of waves and currents, scour holes typically have an asymmetric plane shape that creates unequal soil pressure on each side of the pile, and this pressure difference will have a more unfavorable impact on the pile lateral response than that of a scour hole with a symmetric geometry. In this study, an asymmetric heart-shaped scour hole is defined, and parametric analyses are performed to determine the pile lateral response using a three-dimensional (3D) finite element (FE) method in which the scour hole dimensions and the loading directions were varied. As the scour depth increased from 1.0D to 5.0D, the difference in the reduction ratio between the pile lateral capacities for the two scour hole shapes increased from 0.2% to 7.0%, while the gap in the pile bending moments decreased. Moreover, the results indicated that a heart-shaped scour hole was not sensitive to changes in the side slope angle. The pile lateral capacity was found to be lowest when the lateral load was applied negatively along the y axis; the gap in the pile maximum bending moments for the three loading directions was 90 kN·m, and the gap reduced as the scour depth increased.