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Fluid mud density determination in navigational channels

S. Claeys, B. Dierikx and S. Paul (Dutch Ministry of Infrastructure and Environment) and J. van Reenen (Port of Rotterdam).


For the safe passage of vessel into the ports of Antwerp, Zeebrugge,RotterdamandIJmuidenit is essential that the navigational channels are kept on a predetermined depth, the so called navigational depth (or nautical depth). Because of continuous sedimentation this requires regular dredging.

Depending on the mud rheology (viscosity, rigidity), hydraulic conditions, available tug help and restricted maximum negative keel clearance; vessels can safely maneuver into fluid mud suspensions. The in-situ mapping of this nautical bottom is done by density measurements. Depending on the local lateral and vertical mud condition the relation between the rheology and density is determined giving different density standards. Generally, the density of the fluid mud is less than 1.2 g/cm³ (Dutch requirements).  Therefore a part of the fluid mud layer can be added to the water depth as maneuvering space resulting in the navigational depth. This means that the density of the fluid mud layer as a function of depth must be measured regularly.


In the last few years researchers of the Flanders Hydraulic Research (Flemish Government),  thePortof Rotterdam, the Dutch Ministry of Infrastructure and Environment and third party manufactures have evaluated existing and new methods for the determination of the density of fluid mud Different methods were analyzed on their physical principles, tested in a laboratory and tested in the field. This paper discusses the main results and conclusions.





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