Osaka University
After the nice tour at the research facilities of the Toyo Company, the Civil Engineering department of the Osaka University did some nice presentations. The Osaka University is known for her innovation and is one of the top universities of Japan. During the first presentation by the professor of the Civil Engineering department it became clear that the focus of the university is shifting towards international students. The focus on global scale instead of only national scale was also visible during other previous excursions and in our macro and meso studies. After the introduction of the university, a movie about the highlights of the city was shown.
After the movie, a master student of the university did a presentation about his research. He did research on the development of an effective technique on rubble mound seawall in artificial island under construction. During the construction of an artificial island, the seawall is extra vulnerable for storms and tsunamis. To reduce the vulnerability, research on a steel wire net in the middle of the seawall is executed. This research can be divided into two parts; a model experiment and a numerical simulation. The model experiment is done with help of the water flume, as is described in the visit report of the Toyo construction company. There were two different tests executed, a test with only the rubble mound seawall and a test with the wire net in the middle. This model experiment shows the effect of the wire net clearly. Without the measure, most the material of the seawall was shifted towards the island. The effect of the wire net is that the damage of the rubble mound seawall is more symmetrical and the damage was slightly reduced. The question if the wire net is the most effective measure is not answered yet. The master student did not execute any test with other possible countermeasures, while this can be really interesting.
The second presentation was performed by a PhD student of the university. His presentation was about the tsunami interaction with bay beaches and associated headlands. The study is based on the tsunami disasters of 2004 and 2011. This study is relevant because of the high vulnerability of bays due to storms and tsunamis. The morphology of the beach in the bay is important for the impact that the tsunami will have. Therefore the PhD student looked at different morphological features of the beaches. The focus was on high waves and on tsunamis. The conclusion of the research was that the behaviour of the waves of high waves, with a short wave period, and tsunamis, with longer wave periods, are opposite when the waves interact with the bay and headlands. There was more energy concentrated at the bay areas in the tsunami simulations than in the simulations of high waves. This means that the wave height and the water level in the bay is increased by a tsunami. This has consequences for the damage of a tsunami in the bay. This conclusion is important for city planners to protect the bay and city more efficient against tsunamis and storms.