Dredging method and dredging apparatus

A dredging apparatus comprising

• a case being laid down into a body of water in communication with the atmosphere;
• a suction pipe having a suction portion at a lower end thereof, said suction pipe being connected to said case;
• a dome-shaped cover being provided to the lower end of said suction pipe so as to cover the suction portion:
• a spout pipe whose one end is opened in said dome-shaped cover;
• a spout pump for spouting water, with high pressure, from said spout pipe toward a bottom of said body of water;
• a drain pump for draining water in said case and forming a level difference between a water level in said case and an external water level;
• and
• a container being removably disposed at an intermediate portion of said suction pipe.

A dredging apparatus comprising:

• a cylindrical case pivotably connected to a boat on a body of water so as to allow an up-down movement of said cylindrical case, said case having an upper end, which is opened and in communication with the atmosphere, and a lower end which is closed and laid down into said body of water;
• a suction pipe having an inlet at the lower end thereof, said suction pipe being connected to said case;
• a dome-shaped cover being provided to the lower end of said suction pipe so as to cover the suction portion;
• a spout pipe whose one end is opened in said dome-shaped cover;
• a spout pump for spouting water, with high pressure, from said spout pipe toward a bottom of said body of water;
• a drain pump for draining water in said case and forming a level difference between a water level in said case and an external water level;
• and
• a conveyor extended in said case, said conveyor discharging sand and gravels deposited in said case.