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Dredging is the process by which, either new water channels/waterways are created or existing water channels/waterways are deepened. By Dredging, the water channels/waterways are rendered fit for navigation by ships. Normally dredging is carried out to build new water channels to seaports or maintain existing water channels to seaports. Dredging is carried out by using special ships/equipment called dredgers. Dutch are world leaders in dredging.
Types of Dredging
Dredging is normally classified into two types:
- Capital Dredging: This refers to dredging which is carried out initially to create a new seaport/waterway. Usually, cutter-suction dredgers (CSD) are utilized to carry out Capital dredging. CSDs are floating platforms/pantoons with the necessary equipment to carry out dredging. The dredger has a huge tool called a cutter. Cutter is nothing but a big rod/pipe with a cutter head at the end. This rod can be swung and rotated. When it is brought in contact with the earth bed, it loosens the earth. The mud/sand slurry formed, by loosening of earth, is sucked by the cutter, with help of huge dredge pumps. This slurry is then deposited in nearby land with the helps of pipes or it is filled in barges and then deposited in deep sea. Cutter-suctions dredgers can be stationary or self-propelled.
- Maintenance Dredging: The navigable seaports/waterways get silted with passage of time, due to the sand/mud brought by water currents. This causes the draft/depth of the seaport/waterway to get decreased, rendering the waterways unfit for navigation. Dredging is thus needed again, to increase the depth, to make the waterway navigable. Trailer Suction hopper dredgers (TSHD) are usually utilized to carry out maintenance dredging. The operate similar to vacuum cleaners. TSHDs are nothing but ships with suction pipes and large hollow space called hopper. The hoppers have doors at bottom which can be opened. The maintenance dredging operation consists of lowering the suction pipe such that it touches the sea bed. The Dredge pumps are then operated and the dredger is slowly moved along the path, that needs to be deepened. The suction pipes suck up the mud/sand slurry from the sea bed and fill it in the hopper. The excess water in the slurry is spilled off by sedimentation process. Once the hopper is fully filled with slurry, the suction pipes are lifted up. The TSHD then sails to deep sea and then opens the bottom hopper doors, thus disposing off the mud slurry. Then it returns again to the dredging area to carry on with further dredging.
Top Dredging Companies in the world
- Van Oord Dredging and Marine Contractors bv
- Ballast Nedam
- Royal Boskalis Westminster nv
- Jan de Nul
- Dredging International
- Dredging Corporation of India Limited
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