The breakwater in Hososhima Port will built in the high wave area where significant wave height of offshore wave reaches 13m. With the popular wave dissipating block whose KD value is 8 and slope gradient is 1: 4/3, the calculated result of the minimum mass by Hudson's formula exceeds 200 tons. Concerning the enlargement of the block and application of the high specific gravity block, the three-dimensional hydraulic model experiment was carried out in the plane water tank with the multiple direction random wave generator. Both multiple and one-dimensional random waves were generated and those results were compared to clear the characteristics of one-dimensional experiments.
