| 摘要 |
PURPOSE:To keep off pollution in the underwater, by making dredging work so as to be performed after surrounding the perimeter of a dredging spot on the bottom of the water with a pollution preventing pipe. CONSTITUTION:When dredging takes place, three pipes 12 are made to go down, and each lower end of these pipes is inset in earth and sand on the bottom B and locked thereinto. Afterward, a grab 21 is put in these pipes 12 whereby dredging is carried out in order. And, the pipe 12 completing the dredging is pulled out therefrom after turbidness of water inside the pipe is settled down so that water an and around the dredging spot is in no case muddied.
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