Model experiments and simulations on influence of liquefaction on scour at a landward toe of coastal dykes due to tsunami overflow

Takegawa, N. and Sawada, Y. and Murai, K. and Kawabata, T. (2016) Model experiments and simulations on influence of liquefaction on scour at a landward toe of coastal dykes due to tsunami overflow. In: ICSE 2016 (8th International Conference on Scour and Erosion), 12-15 September 2016, Oxford, UK.

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Abstract

In the 2011 off the Pacific Coast of Tohoku Earthquake, massive tsunami caused serious damage to coastal dykes. One of the failure mechanisms of a coastal dyke has been considered as the local scour at the landward toe of a coastal dyke. Furthermore, there is a possibility that liquefaction occurs around a coastal dyke by aftershocks when tsunami strikes. In this paper, flume experiments were conducted to clarify the influence of liquefaction on the scour at a landward toe of coastal dykes due to tsunami over flow. Moreover, simulations were conducted to evaluate the influence of the upward seepage on the scour. In the experiments, scour process and scour profile is different according to the degree of liquefaction. In the simulations, the vertical velocity at the bottom of scour hole increases by the upward seepage. However, there is little influence of the vertical velocity on the scour because the uplift force of the vertical velocity is small.

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