This thesis investigates the collision force of driftwoods and small boats due to tsunamis. Even though there are some calculation formulas from past experiments, quantitative approaches for design criteria of tsunami protection structures are not established. Accordingly, to upgrade design criteria of tsunami protection structures, the thesis aimed to investigate into an adaptability of the formulas obtained past researches and new experimental evaluation formula derived from present research comparing with the measurements of hydraulic model experiment.
On March 11, 2011, Tohoku - Pacific Coast Earthquake tsunami struck a large area on the Pacific coast, especially from Chiba Prefecture to the coastal areas of Aomori Prefecture, where the damage to coastal structures was so great, not only port facilities, but also shore protection facilities such as breakwater, seawall, and sea embankment. In particular, the area around the Fukushima Daiichi nuclear power plant suffered from the damage generated by radiation leak due to tsunamis.
On the other hand, it was confirmed that the Kamaishi bay-mouth breakwater delayed reaching tsunami in the bay and had the effect of reducing the tsunami height. In the shore protective facilities such as breakwater, it is considered to have protective effect on the tsunami(Hiraishi et al., 2011). Accordingly, it is necessary to make the shore protective facilities tenacious structure that can withstand the port structure without collapsing even for the largest scale tsunami.
In this way, this report investigates the collision force of driftwoods and small boats due to tsunamis. Even though there are some calculation formulas from previous researches, quantitative approaches for design criteria of tsunami protection structures are not established. Accordingly, to upgrade design criteria of tsunami protection structures, the research aimed to investigate into an adaptability of the formulas from previous researches and new experimental evaluation formula derived from present research.
In this paper, to compare the measurements with the calculation formula, we have a hydraulic model experiment. With regard to small boat, we use the measurements of experiment conducted in 2017 and of similar experiments conducted in 2016(Okura, 2017) and 2015(Ono and Hiraishi, 2017) as well in this experiment. In contrast, with regard to driftwood, we use the measurements of similar experiments conducted in 2016 and 2015.
