Breakwater Foundation Reinforced with Sheet Pile

Waterfront structures such as sheet pile breakwater, coastal dike, sea wall, etc., suffer serious damage from the earthquake and tsunami. The sheet pile 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 sheet pile breakwater mound/foundation which was caused due to collapse of the sheet pile 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 sheet pile 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 sheet pile breakwater foundations which will make the sheet pile breakwater resilient against the earthquake and tsunami forces.

This paper deals with the development of an effective reinforcement technology for sheet pile 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 sheet pile 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 steel sheet pile and gabion under earthquake loading and its influence on sheet pile breakwater performance was made clear.

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