Abstract
Coastal dikes in Iwate, Miyagi, and Fukushima prefectures were seriously damaged due to the tsunami overflow by the 2011 off the Pacific coast of Tohoku Earthquake. However, hydrodynamic forces acting on the landward toe protection works were not clarified at present state. Therefore, hydrodynamic pressure of the dike slope and hydrodynamic force of the landward toe protection works due to tsunami overflow were experimentally investigated using different types of coastal blocks. The obtained results show that uplift force of the landward toe armoring block does not proportionally increase with the increase of tsunami height. Although surface protuberances of blocks of landward toe bed protection works increase the hydrodynamic force, they have the effect to reduce the velocity related to scouring. On the other hand, stepwise armoring blocks have the effect to decrease hydrodynamic force and reduce the velocity over the landward toe protection blocks.
