Centrifuge modelling for stability evaluation of a breakwater foundation subjected to an earthquake and a tsunami

Many breakwaters were failed due to the geo-disaster caused by the 2011 off the Pacific Coast of Tohoku Earthquake and Tsunami. Investigations were carried out, and it was found that the breakwater failed mainly due to the failure of its foundation. However, mechanism of the failure of the breakwater has not yet been completely explained. This paper focuses on the stability evaluation of a breakwater foundation subjected to an earthquake and a tsunami. The main feature of the study is application of centrifuge technique for a geo-disaster caused by an earthquake and a tsunami. Results of the study show that in the case of a geo-disaster brought by an earthquake and a tsunami, excessive pore water pressure generated in the sandy ground, and consequently liquefaction occurred during the earthquake. That resulted in deformation of the foundation ground and settlement of the breakwater. During the tsunami, scouring could occur around the harbor side mound, and seepage took place beneath the breakwater. These were the main reasons of decrease in bearing capacity of the foundation ground and failure of the breakwater. Numerical simulations were also performed to make clear the mechanism and behavior of the breakwater under an earthquake and a tsunami. Overall, this study can be useful to understand the failure process of a breakwater under an earthquake and a tsunami, and it can be helpful to develop countermeasures in order to reduce the earthquake and tsunami induced damage of a breakwater in the future.