107 / 2025-04-24 12:56:07

Experimental Investigation of Scour Effects on Regular and Breaking Wave Loads on a Monopile

wave load; regular wave; breaking wave; monopile; local scour.

This study conducted a series of model tests to assess the changes in wave loads on monopile foundations during the scouring process. The wave forces on the pile were determined by measuring the strain along the depth-distributed fiber Bragg grating. When subjected to regular waves, the horizontal loads on the pile above the original mudline are minimally affected by scour. However, scour amplifies the lateral shear forces and moments on the pile body within symmetric scour holes. In asymmetric scour pits, the partially submerged pile body experiences wave-induced shear forces in the wave and lee directions influenced by active and passive soil pressures, respectively. Based on wave theories and the Morison equation, a novel approach incorporating the increased wave force area within scour holes is introduced to evaluate the horizontal wave forces on a monopile under scour conditions. The breaking wave loads comprise quasi-static and impact forces. A new method for dividing quasi-static and impact forces based on the characteristics of wave motion is developed. Comparative analysis indicates that the impact coefficient is minimally impacted by scour, and the behavior of quasi-static wave forces under breaking wave resembles that under the regular wave.