Abstract
After the Tohoku earthquake in 2011, coastal dikes are required to be improved their tenacity against tsunami disaster. And it is reported that scours of coastal dikes caused by tsunami overflow were mainly occurred at the toe of the leeward slope. Therefore, we have proposed a weir-type countermeasure in order to reduce the erosion of coastal dikes. In this study, the movable-bed hydraulic physical experiment was conducted to confirm the function of the countermeasure which reduces the erosion of dikes from the tsunami overflow. As a result of the experiment, it is confirmed that the weir-type countermeasure significantly reduces and delays the dike erosion. It means the proposed weir-type countermeasure contributes to improve tenacity of coastal dikes against tsunami disaster. However, it is shown that the weir-type countermeasure increases the dike erosion when the height of the countermeasure is relatively larger compared to height of the tsunami overflow. The applicable height of the countermeasure should be investigated in the future work. Moreover, the tsunami force acting on the countermeasure is about 1.2 times larger than the hydrostatic force during the tsunami overflow.
