| 摘要 |
PROBLEM TO BE SOLVED: To provide a thin-layer dredging method by which diffusion of sediment in dredging work can be suppressed with a simple structure and only sediment components of small particle diameters can be dredged.SOLUTION: A dredging device 1 comprises: a tubular container 3, which is bottomed and has a tubular shape, disposed in water so as to be movable while projecting its upper end opening on the water; and a suction tube 5 of which one end is inserted into and communicated with the inside of the tubular container 3 and the another end is inserted into a face of a bottom of water. According to a thin-layer dredging method, the dredging device 1 is used to make a water level H inside of the tubular container lower than a water level outside of the tubular container and generate negative pressure within the suction tube 5 utilizing a water head difference between the water levels inside and outside of the tubular container 3, thereby sucking sediment on a top layer of the bottom of water. A flow velocity V within the suction tube 5 is measured by flow velocity measuring means and the flow velocity B within the suction tube is controlled to be equal to or lower than a required flow velocity by flow velocity control means based on the measurement obtained by the flow velocity measuring means, thereby sucking only sediment components with diameters equal to or smaller than a required particle diameter. |
