RIASSUNTO
Abstract
Tsunami wave attacks are becoming an increasingly common phenomenon. A huge tsunami sometimes causes severe damages for wide coastal areas, i.e. collapse of cars, ships, boats, houses and even buildings. In many cases, obstacles may be swept away by the run-up tsunami, which carries floating debris, such as car, ship, house and wood, and increase damages on surrounding buildings in a downtown. Recent research works have highlighted the debris impact due to drifting obstacles caused by tsunami force, which is very difficult to be evaluated and predicted accurately. To estimate a tsunami impact including an impulsive pressure acting on both buildings in a populated zone and floating structures, this study has proposed and developed a hybrid method combining the Smoothed Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM). The numerical results were validated by relevant experimental results. To clarify the effects of the tsunami attack angle, arrangement of building and shaded zone, this model was also applied to the interaction between tsunami waves and a simplified town consisting of a grid arrangement of buildings, as well as the Hiroshima downtown in a real scenario. The characteristics of impact force caused by a floating obstacle was also examined.
Introduction
Nowadays, earthquakes frequently occur across the world and they cannot be predicted with satisfactory precision. A significant earthquake in ocean results in a high possibility of tsunami wave generation and inundation. Many countries have already suffered from the impact of tsunamis, particularly in their coastal regions.
According to the research by National Tsunami Hazard Mitigation Program (2001), there are seven principles for planning and designing area that is vulnerable to tsunamis. The cabinet office of Japanese government also published a design guideline for tsunami evacuation buildings. Fukuyama (2013) evaluated these guidelines using recent tsunami events. Nakamura (2010) performed numerical and experimental works by using the Fluid-Sediment Interaction Model (FSM) to investigate the tsunami run-up and the tsunami force acting on a square onshore structure. In order to calculate the force and impact pressure caused by tsunami waves on a single building, several numerical models and experimental works have been developed by Mutsuda, et al. (2013a, 2013b, 2014 and 2015).Moon (2014) performed an experimental work to evaluate the pressure acting on a simplified onshore building. Wei et al. (2015) investigated the impact of tsunami bore on simple bridge piers.