Reinforcing foundation model to mitigate earthquake induced failure of breakwater: Model tests and numerical simulations

Breakwaters are commonly used to protect the ports and harbours from destructive effects of sea waves, typhoons and tsunamis. In the past few decades, it was observed that breakwaters are vulnerable to earthquake and tsunami. Many breakwaters were collapsed by the 2011 off the Pacific Coast of Tohoku Earthquake and subsequent tsunami. The breakwaters were damaged mainly due to failure of their foundations. Therefore, countermeasures are urgently needed for the foundation of breakwater in order to make the breakwater safe against these destructive forces. This paper deals with the effective reinforcing countermeasures for foundation of a breakwater which can provide resiliency to the breakwater against earthquake induced damage. Sheet piles and gabions were used for reinforcing the foundation. In order to evaluate the effectiveness of the reinforced foundation under earthquake loadings, a series of shaking table tests were performed under 1 g gravitational field, and comparisons are made between the reinforced and the conventional foundation of breakwater. Numerical simulation was performed to elucidate the mechanism of the reinforcement-soil-breakwater system under different earthquake loadings. Through the tests, it was observed the reinforced foundation performed well in reducing the damage of breakwater caused by earthquake induced forces. This study can be useful for researchers and practice engineers to establish countermeasures in order to reduce the damage of breakwater caused by earthquakes in the future.