Rheological Analysis of Mud: Towards an Implementation of the Nautical Bottom Concept in the Port of Hamburg

The nautical bottom (the level at which contact with a ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability of a ship) should be associated to a measurable physical characteristic. Bulk density is typically used as a criterion for nautical bottom by many ports worldwide. However, the rheological properties particularly the yield stress of mud would be better parameters for defining a criterion for nautical bottom due to their strong correlation with the flow properties of mud and navigability. The density-yield stress correlation depends significantly on different parameters of mud such as organic matter type and content, clay type and content, particle size distribution and salinity. Therefore, a single critical value of density cannot be chosen for the nautical bottom criterion in a port like Port of Hamburg, where the above mentioned parameters are varying from one harbour location to another. This justifies the need for a study of the rheological properties (yield stress) of mud in Port of Hamburg.