Armor Damage on Harbor-Side Rubble Mound of Composite Breakwaters Against Water Jet Caused by Impinging Bore-Like Tsunami

Abstract

A series of hydraulic model experiments was systematically and carefully carried out to estimate the stability of various types of armor units for a harbor-side rubble mound of a composite breakwater against a water jet caused by an impinging bore-like tsunami. Armor stones of weight 1 ton were seen to be easily removed by the tsunami flow. Flat type concrete blocks with well-arranged holes showed high stability. In the case of using wave-dissipating blocks, the total stability of the armor layer was enhanced by placing heavier blocks along the toe of the slope. Numerical analysis was also carried out to investigate the effect of the shape of the blocks. The computed time series of water level and the behavior of the impinging jet agreed well with the experimental ones. The computational result of hydrodynamic forces acting on armor blocks revealed that the uplift forces were largely decreased by the holes in the blocks.

Estimation Method of Armor Stability Against Tsunami Overtopping Caisson Breakwater Based on Overflow Depth

“…With regard to the numerical computation of the tsunami overtopping the caisson, Maruyama et al [2012] adequately reproduced the laboratory experiment of an overtopping jet from tsunami by using the volume of fluid (VOF) method implemented in the OpenFOAM CFD model [OpenCFD Ltd., 2011]. In the case of the steady overflow of tsunami, however, the computation result using the VOF method did not reproduce well due to the excessive entrainment of air into the impinging jet.…”

Numerical Analysis on Stability of Caisson-Type Breakwaters under Tsunami-Induced Seepage

“…Two dimensionless coefficients a 0 and b 0 are constants and determined according to experience. In this study, a 0 and b 0 were given as 1500 and 3.6, respectively, according to the past study [11]. In this simulation, a model of sandy seabed was ignored since it can be assumed that the permeability of sand is greatly lower than that of rubble mound and the seepage flow hardly occurs through the seabed.…”