Cutter Dredger

 

General information
A Cutter Suction Dredger (CSD) is an efficient structure for precise dredging in hard soils and shallow water. It is usually kept on position with a spud pole and the dredging is performed by a rotating cutter head at the end of a hinged ladder which is lowered to the seabed. The CSD’s rigid spud system is capable to keep the cutter accurately in the breach, even in hard soils. A disadvantage of the spud is that it makes the CSD a mass spring system in the horizontal plane, with natural periods within the wave period regime. Large dynamic spud reactions are the consequence. When the cutter is in the breach, pitch motions cause the cutter to pound into it, leading to problems like slack ladder hoist wire, stalling cutter drive and even damage of teeth or blades. On top of that, handling of the swing wire anchors, auxiliary boat operations and floating discharge line will put other restrictions on the operability of the CSD.

 

Services & Activities
The Offshore Department has developed the DREDSIM simulation program to simulate the behaviour of Cutter Suction Dredgers in waves. It allows the analysis of the motions of the CSD and the related spud pole and cutter head loads (based on an soil model), combined with a downtime analysis in a certain environment. It is used regularly for clients that want to determine or optimise the operability of their vessels. Also model tests can be carried out, modelling the details of the stiffness of the spudpole and ladder systems.

The Trials & Monitoring Department has been involved in full-scale measurements on Cutter Suction Dredgers. CSD motions and spul pole loads can be measured and analysed.

MARIN's nautical simulator centre MSCN developed a Dredging Simulator the training of the operators of Cutter Suction Dredgers. This included a production model.

 

Facilities & Tools
Cutter Suction Dredgers are tested in the following MARIN facilities :

 

• Shallow Water Basin: model tests in combined waves and wind
• Offshore Basin: model tests in combined current, waves and wind
• Seakeeping and Manoeuvring Basin: model tests in waves
• Deep Water Towing Tank: calm water towing tests

The behaviour of Cutter Suction Dredgers can be simulated using the following tools :

 

DREDSIM: Simulation of the behaviour of cutter section dredger operating in waves
DIFFRAC: 3-D potential theory including wave diffraction
DRIFTP/DBDRIFT: Second order wave excited (drift) forces
LIFSIM/LIFMOT: Analysis of multi body dyamics and lift operations

Software Sales
Some software tools are available for commercial use outside MARIN. A complete overview of these software tools for sale can be found under Software Sales.

 

Experience record
The list below gives a review of Cutter Suction Dredgers projects carried out at MARIN :

 

• Seakeeping tests for a self-propelled Cutter Suction Dredger (IHC Holland, 2004)
• Analysis of the full scale measurements on the Cutter Suction Dredger ‘Oranje’ (Boskalis, 2002)
• Simulations on a Cutter Suction Dredger at 3 waterdepths (Jan de Nul, 2002)
• Model tests and Simulations on the Cutter Suction Dredger HAM 220 (HAM/IHC, 2001)
• DREDSIM development in the Joint Industry Project ‘Workability of Dredgers in waves’ (1998-2000)

Most recent papers on Cutter Dredgers presented by MARIN
(complete overview can be found under Publications)

 

Downtime Analysis Techniques for Complex Offshore and Dredging Operations
van der Wal, Remmelt and de Boer, Gerrit, OMAE Conference, Vancouver, 2004

Downtime Analysis Methods for Offshore Dredging Operations
G.J. Grundlehner (Boskalis), R.J. van der Wal and G.J. de Boer(MARIN), CEDA Conference, Amsterdam, 2003

Prediction Downtime of Dredges Operating in the Open Sea
J.E.W. Wichers and E.J. Claessens, WEDA Conference, Rhode Island, 2000

Most recent articles on Cutter Dredgers written for MARIN Report
(complete overview can be found under Publications)

 

So far no entries have been published.

Contact
For more information on how MARIN can help your organisation with Cutter Suction Dredgers, please contact:

For model test and simulation activities: Offshore Department
For full scale measurements: Trials and Monitoring Department
For nautical training : MSCN