Stability evaluation on the block reinforcement for Tsunami resilient breakwater

In order to improve the stability of breakwater due to overflow and seepage flow under tsunami condition, a series of hydraulic model experiment for the model of Kamaishi Harbor Mouth Breakwaters was conducted in terms of the dimension of block reinforcement such as weight, open ratio and layout pattern. As the result from this study, following conclusions were obtained. 1) This paper proposed a formula to calculate the stable weight of block reinforcement on the breakwater foundation in consideration of the overflow and seepage flow induced by tsunami based on the theoretical force balance among the frictional resistance of block reinforcement, the tractive force of the water flow over the caisson to the block reinforcement and seepage force thorough the breakwater foundation. 2) It is experimentally confirmed that seepage failure of rubble mound on the harbor-side of breakwater firstly occurred and then the damage of breakwater was acceralated after overflow occurred. The proposed formula is effective for evaluating seepage failure and scouring of rubble mound under tsunami condition. 3) The damage of breakwater becomes smallest when the block reinforcements are disposed with the height ratio of 3/4 and the triangulate layout.