Application of SPH-DEM coupled method to failure simulation of a caisson type composite breakwater during a tsunami

Abstract During the 2011 Mw9.0 Tohoku Earthquake, caisson breakwaters in several ports experienced severe tsunami damage. Such failures were probably caused by a combination of scouring and seepage destruction of foundations and by large horizontal forces caused by the tsunami. We use a coupled Smoothed Particle Hydrodynamics (SPH) – Distinct Element Method (DEM) analysis method based on locally averaged equations of motion to analyze scouring and seepage flow phenomena at caisson-type breakwaters during the tsunami. Permeability tests and numerical simulations verified the coupled analysis methods that calculate the forces between solid and liquid phases. Numerically simulated triaxial tests determined the numerical parameters. Experimental simulations of caisson-type breakwater failures under centrifugal conditions validated the numerical method. Numerical simulations of the collapse process in the breakwaters agreed fairly well with experimental results at centrifugal acceleration fields. Thus, the SPH-DEM analysis method is applicable for predictions of collapse or failure in composite type breakwaters during a tsunami.