Study for stability of armor concrete blocks covering coastal dikes for over flow in tsunami

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Kuniaki Oi, Kenjirou Hayashi, Tuyosi Tada, Yoshihisa Miyata

Thursday 2 july 2015

16:15 - 16:30h at Europe 2 (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Adaptation measures

Parallel session: 13K. Floodrisk - Adaptation

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In 2011, a tsunami caused by an earthquake off the Pacific coast of Tohoku seriously caused great damage to many coastal structures. It is important to reinforce these coastal structures with the concrete blocks and to give the function of tenacious structures. In case of coastal dikes, the stability of concrete blocks and the damage of coastal dikes may be affected by the fluid forces acting on the concrete blocks armoring on slope just near the crest of dike in the side of land for the overflow in tsunami. The stability of blocks is also affected by the types of blocks and there geometrical arrangement. The damage of these coastal structures are also affected by the strength of foundation in spillway. Hydrodynamic laboratory experiments were carried out in a wave flume 40m long, and 0.8m wide for the damage of concrete blocks armoring on the slope in side of coastal dike for the over flow in tsunami. The force and bending moment acting on a concrete block just adjacent to the crest of the dike are measured by using a multi component load cell. The velocity distributions around this concrete block are measured by using a Laser Doppler anemometer with 2 velocity components system. The relationship between the velocity distributions on the concrete blocks and pressure distributions on the mound of slope are obtained. The relationship between the fluid forces and overturning moment Mot acting on a concrete block adjacent to the crest of dike in the side of land are also obtained. In the case of overturning bending moment Mot exceeds the resistance bending moment caused by the weight of concrete block, the concrete block turns over from the slope of coastal dike.