Masatoshi IKEUCHI

Study on influence by water falling position on breakwater

Tokuzou HOSOYAMADA

It is reported that the breakwater has been collapsed by the Tsunami of the Great East Japan Earthquake. In other words, the damage caused by the tsunami was revealed to have increased by this. As a countermeasure, it was prescribed to set armorblocks and increase mounds. However, recent studies have reported that armorblocks and mounds damage caused by other than the tsunami.
For this reason, in this research, We propose a structure that extends the end of caisson structure to make the water falling position farther away. The research conducted a two dimensional hydraulic model experiment to verify whether damage to the armorblocks and mound can be reduced. The experiment model was 1/110 scale of the K port breakwater, and the extension structure was set to +100mm, +150mm, +200mm. Also, we made a hole in the extension structure and verified whether damage could be reduced. In addition, experiments were carried out by pumps, with five kinds of flow rates. There were three types of water level. Also, the experiment was repeated twice.
As a result, it found that damage of armorblocks and mound can be reduced by extension structure. And, by providing a hole, damage could be more reduced.
In order to verify the reproducibility of the experiment, the reproduction simulation by the particle method was carried out. The particle method was ISPH method of accurate particle method. As the simulation result, reproducibility of the experiment could be confirmed and water dispersion from the hole could be confirmed.
This proposed structure does not need to increase the rigidity and can be retrofitted to the existing structure, so it can be expected as a new breakwater structure.