Takaki Daichi

A Study on Stability Evaluation of Coast Breakwater against Tsunami

Ohtsuka Satoru

In the Great East Japan Earthquake that occurred in 2011, many caisson breakwaters were damaged by the tsunami. Characteristics of the breakwater damage include not only the sliding movement of the caissons pushed by the water level difference inside and outside the harbor, but also the action of penetrating water in the mound and the scooping waves scoured the mound inside the harbor side. Evaluation of supporting force against vertical and horizontal load at the time of the Tsunami incidents, influence of osmotic force and the caisson's ground support resistance have not been clarified and the caisson reinforcement method and stability evaluation method have not been established either.
�@In this study, the rigid plastic finite element method was used as an analysis method. We reviewed physical property values used in past research and analyzed using new property values. From the analysis results, large strain occurred from both ends of the lower part of the caisson to the lower part of the mound slope. Moreover, it was confirmed that the mound behind the caissons was pushed out in the direction of load advance, and the same destruction form as the model experiment was confirmed. In all cases than the supporting force, the same supporting force as the experimental result was obtained, and in the model with the water level difference in particular, regardless of the penetration force, equivalent bearing power was obtained. From the above, it was clarified that by using the rigid plastic finite element method, it is possible to rationally and appropriately evaluate the fracture phenomenon of the caisson supporting ground despite the fact that there is no influence of a small number of ground constants and stress histories.