Abstract
A block mound seawall, constructed on a reef that follows a steep slope of 1/7 at K-Port in M-Island, was strongly damaged by storm waves in 2009. Most wave dissipating blocks were scattered by the action of plunging breaking waves, and the apron behind the seawall was collapsed by the overtopping waves. Hydraulic model tests using random waves were conducted with the model scale of 1/50 to reproduce the damage of the block mound seawall. The wave overtopping flow rate at the site of the damage was found to be more than 10-2 m3/m/s, which is the stability limit of port facilities. The relationship between the number of wave actions and the block damage ratio on the reef was discussed based on the results of block stability tests, and the correction factor for Hudson's formula was newly proposed for several reef width conditions. In order to decrease the wave overtopping flow rate, it is necessary to raise the upright section of the seawall by 2 meters. It was also shown that the present block size of 20 tons was insufficient, and the necessary block size was 80 tons.
