Insights into Effects of Seepage on Failure of Breakwater Mound: Experimental and Numerical Investigations

Identifying the collapse mechanism of a breakwater mound caused by overtopping and seepage during extreme natural disasters is an essential element of a hazard mitigation policy. This research study conducts a set of experiments to quantify the effects of seepage and overtopping on the scouring of a breakwater. A scaled model of the Kamaishi breakwater in Japan, which was significantly damaged by the 2011 Great East Japan earthquake, is chosen for the tests. The experimental study reveals the significant influence of the hydraulic gradient of a breakwater on accelerating the depth of scouring. Then, a series of numerical simulations using smoothed particle hydrodynamics are carried out to justify the experimental outcomes and extract buried information which is normally not possible to be obtained from the experiments. Also, two countermeasures verified by the experimental and numerical models reveal significant reductions in the depth and width of scouring in a breakwater mound.