Rheological analysis of mud from Port of Hamburg, Germany

Ahmad Shakeel,Claire Chassagne,Alex Kirichek

doi:10.1007/s11368-019-02448-7

Ahmad Shakeel, Claire Chassagne + Show 1 more

Open Access

https://doi.org/10.1007/s11368-019-02448-7

Copy DOI

Abstract

PurposeAn innovative way to define navigable fluid mud layers is to make use of their rheological properties, in particular their yield stress. In order to help the development of in situ measurement techniques, it is essential that the key rheological parameters are estimated beforehand. Is there only one yield stress? In which shear rate/shear stress range is yield expected to occur? How is yield stress dependent on depths and locations in the harbor? In order to answer these questions, we investigated the changes in the rheological properties of mud from along the river stream in the Port of Hamburg, Germany, using a recently developed laboratory protocol.Materials and methodsIn this study, a detailed rheological analysis was carried out on the mud samples collected from different locations and depths of the Port of Hamburg. A variety of rheological tests was performed including: stress sweep tests, flow curves, thixotropic tests, oscillatory amplitude, and frequency sweep tests.Results and discussionThe yield stresses of sediments from different locations were significantly dissimilar from each other due to differences in densities and organic matter content. Two yield stresses (termed static and fluidic) were observed for every sample and linearly correlated to each other. The thixotropic studies showed that all mud samples, except from one location, displayed a combination of thixotropic and anti-thixotropic behaviors. The results of frequency sweep tests showed the solid-like character of the sediments within the linear viscoelastic limit. The yield stresses, thixotropy, and moduli of the mud samples increased by going deeper into the sediment bed due to the increase in density of the sediments.ConclusionsThis study confirmed the applicability of the recently developed protocol as a fast and reliable tool to measure the yield stresses of sediments from different locations and depths in the Port of Hamburg. The fluid mud layer, in all the locations it was observed, exhibited relatively small yield stress values and weak thixotropic behavior. This confirms that despite the fact that rheology of fluid mud is complex, this layer can be navigable.

Highlights

Mud is a cohesive material which contains predominantly clay minerals, water, organic matter, and some amounts of silt and sand
The mud samples obtained from the RT location displayed higher values of yield stresses (57–312 Pa) with the comparatively lower values of densities (1154–1210 kg m−3) due to their higher organic matter content (4.1–4.3%)
A detailed rheological analysis was performed on the mud samples collected from different locations of the Port of Hamburg, Germany, representing different layers within the sediment bed

Summary

Introduction

Mud is a cohesive material which contains predominantly clay minerals, water, organic matter, and some amounts of silt and sand. Fluid mud is usually defined as a fluid having a density within the range of 1030–1300 kg m−3, in which settling is considerably hindered by the presence of flocs (Inglis and Allen 1957; Whitehouse et al 2000; McAnally et al 2007a). It has been shown that rheological properties are dependent on the mud density, and that the presence of small amounts of organic matter is affecting the cohesion and rheological behavior significantly (Paterson et al 1990; Paterson and Hagerthey 2001; Tolhurst et al 2002; Wurpts 2005; Malarkey et al 2015; Schindler et al 2015; Parsons et al 2016)

Objectives

Methods

Results

Conclusion