In this study, numerical simulations for the Tohoku-Pacific Ocean earthquake tsunami are executed to reproduce the tsunami disaster in the Haramachi port. The configuration of main breakwaters which consists of trapezoidal caisson with sloping top seemed to suppress a devastating damage due to the tsunami. So not only the trapezoidal caisson but redesigned square type breakwater is assumed and compared through the numerical computing to inspect wave force around the breakwaters and current

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... on the block mounds. Pushdown force on the sloping top restricts caisson sliding and armor blocks with large void ratio decrease uplift pressure. In addition, height of the trapezoidal coping position taller than that of square coping turns out to weaken the overtopping flow into the block mound not to cause the mound scour.