Numerical study on suppression of tsunami with under-sea breakwater

Abstract

Large-scale tsunami occurs every 100 or 150 years statistically, and 95% of these tsunami lead to great disasters which kill over 1,000 people. In order to avoid, suppress or mitigate such damage, it is necessary to perform a risk management from the point of view of disaster prevention engineering. There are breakwaters as one of existing measures for tsunami, and the effectiveness of breakwaters has been demonstrated. However, a conventional breakwater can be disrupted by the impact of tsunami, and then it turns into debris that causes to expand the damage. There is also the problem of impairing the landscape by locating a large-scale breakwater along a sea shore. Construction of under-sea breakwaters is one possible way to coping with these problems. In this paper, tsunami behavior when the under-sea breakwater is located is numerically simulated using MPS method, which is one of the particle methods. And the effectiveness on suppression of tsunami with the under-sea breakwater is researched and verified. Through the present study, it was confirmed that the under-sea breakwater can suppress tsunami. The higher the under-sea breakwater is, the more it suppresses tsunami. However, if the height of the breakwater is too low, the effect on tsunami suppression is small. In addition, it was found that, by setting under-sea breakwater at a suitable position, arrival time of a tsunami can be delayed.