Study on local scouring of gravel mound due to tsunami overflow

Many breakwaters were damaged due to tsunami actions in Tohoku earthquake in 2011. The local scouring of the gravel mound at the foot of the breakwater was reported as one of the typical failures. This local scouring on the gravel mound is assumed due to a large vortex formed by the tsunami overflow. The purpose of this study is to clarify the characteristics of local scouring under several tsunami overflow conditions. This study conducted hydraulic experiments and numerical simulation. The scale of the scouring mainly depends on the overflow condition, gravel diameter, and water depth above the mound. This study proposed some experimental equations that estimate the maximum scoured depth and the width of the scoured topography. Numerical simulation based on SPH, Smoothed Particle Hydrodynamics, was employed in this study to clarify the interaction between the large vortex flow on the gravel mound and the deformation of the mound.