Numerical Simulation of Damage to a Soil Embankment from Tsunami Overflow
Hiroyuki Fujii*,**, Shintaro Hotta**, and Nobuo Shuto**
*Department of Coastal Engineering, INA Corporation, 8-4-1 Toshima, Kita-ku, Tokyo 114-0003, Japan
**Advanced Research Institute for the Sciences and Humanities (ARISH), Nihon University 6F Ichigaya Tokyu Building, 4-2-1 Kudan-kita, Chiyoda-ku, Tokyo 102-0073, Japan
There have been many studies on tsunami forces acting on structures, but few studies on tsunami-induced water flows that move a lot of sands or soils, resulting in damages to such structures as road embankments and seawalls. In the present study, the damage of soil embankments by tsunami overflow is discussed. Hydraulic experiments on movable beds reveal that the erosion of the downstream slope and the scouring at the rear toe are important factors in the erosion of soil embankments. An erosion rate law is experimentally established. Current velocity measured on a fixed bed verifies the application of the CADMAS-SURF to the present situation. A numerical method to simulate the erosion of soil embankments is developed using these data. It is applied to gain insight into the Shuto diagram (2001) about the damages of embankment obtained from field data for local tsunamis of short wave period in the past. Among six tests, reasonable agreements were obtained in four cases. In other two cases, the method gave the larger erosion than the expected ones from the diagram.
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