The hopper dredger Kairin Maru is installed with pressure water equipment for the preparation of soil to be dredged, and a field test was conducted to investigate the effect of its equipment. Since the test seems to have carried out against soft surface materials with the N value of less than 20, its actual dredging capacity against firmly packed sand was not made clear.
　The result of this test, however, will suggest to us toconclude that both pressure water for the preparation of soil to be dredged and the ship's speed have a great influence upon the production of a hopper dredger.