Technologies and Solutions

High Concentration Bottom Mud Dredging Construction Method: KAREN Method

Dredging and disposal of bottom mud deposits, for example in ports, lakes, and marshes, have become indispensable for preventing eutrophication of the waters and protecting the natural ecosystem and the human living environment.

The KAREN Method enables high concentration dredging without pollution of the surrounding waters by using a rotary shaver dredging system which removes bottom mud in a condition close to its deposited state. 

High Concentration Bottom Mud Dredging Construction Method: KAREN Method

Dredging Procedure

· The bottom cutting blade of the dredging machine is set at the target depth.
· Removal of bottom mud by the rotary shaver begins, with shovel operation synchronized to the swing speed of the dredger.
· Together with the start of swinging, the bottom cutting blade takes up the set thickness of bottom mud.
· Slurry taken into the casing is pumped to a shipboard storage tank by a submerged sand pump, and is then conveyed to the disposal site by a pressure pump.


  • Possible to dredge bottom mud with high water content, like sediments in lakes and marshes, while suppressing the spread of turbidity.
  • High concentration dredging is possible by using a mud collector with an auxiliary mud suction function in the mechanical cutting mechanism.
  • Dredging accuracy is improved by an operation control system that enables fully automatic operation and a ship positioning system utilizing GPS.
  • The dredging depth and soil thickness are measured by an ultrasonic probe device, the condition of mud conveying is monitored by a densimeter, and the ship’s position is determined by the automatic positioning system, all in real time, enabling appropriate operation control.
  • Bottom mud can be pumped in a highly concentrated state directly to the disposal site by long distance mud conveying up to approximately 5km.