Waterfront structures such as breakwater, coastal dike, sea wall, etc., suffer serious damage from the earthquake and tsunami. The breakwaters are designed to protect coastline and seaport from the devastation effect of wave and current of tsunami by absorbing their wave energy and reducing overtopping.

The port of Kamaishi (Iwate Prefecture, Japan) suffered heavy causalities due to the Great East Japan Earthquake in March 2011 mainly due to the damage of breakwater mound/foundation which was caused due to collapse of the breakwater. On the other hand, mitigation of compound disaster due to predicted future earthquakes such as Tokai earthquake, Nankai Earthquake, and Tonankai-Nankai Earthquake is a matter of great concern.

The stability and safe performance of breakwater is very important for the protection of structures and population living near to coastline. It is, therefore, necessary to develop a new earthquake and tsunami resistant reinforcement technique for breakwater foundations which will make the breakwater resilient against the earthquake and tsunami forces.

This paper deals with the development of an effective reinforcement technology for breakwater foundation which provides resiliency to the mound against earthquake. The technique involves use of sheet pile and gabion type mound (gravel wrapped up in steel wired mesh), which is effective in preventing breakwater subsidence and horizontal displacement. As a part of the study, a series of shaking table test in 1 g of gravitational field were performed and through the tests, the reinforcement effect by the sheet pile and gabion under earthquake loading and its influence on breakwater performance was made clear.

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