Evaluation of Houska Thixotropic Model for Quantification of Shear and Time Dependency of Different Mud Types
Type:
Presented during:
CEDA Dredging Days 2021
Authors:
A.M. Talmon, E. Meshkati, T. Lelieveld and A.P.K. Goda
Abstract
Soft sediment such as mud is a prominent material encountered in dredging. The muds are everywhere: from muddy coasts with sand shortages, fluid mud layers in waterways and ports, to dredged muds and muds in resource industries deposits in reclamation and rehabilitation projects and so on. Although they seem similar in composition, their slight differences (e.g. in clay minerology) result in remarkable rheological differences between them. Moreover, muds undergo different hydraulic and geotechnical conditions (prior and) during dredging operations, by which their rheological properties may drastically vary subject to applications. Effect of time on flow and deformation behaviour of mud is of importance which is not well understood. The clays in muds do not only impart general non-Newtonian influences such as yield and viscous characters but also time-dependent influences, known also as thixotropic properties of mud.
The rheological characterization of soft sediments is a field of science on its own where parameter values are established by rheometry. Despite that this provides several opportunities for detailed interpretations, one needs to be aware of limitations in rheological testing, typical flaws and appreciate the level of sophistication of the characterizations with respect to their application.
This paper is an attempt to shed light on the time-dependent rheological behaviour of two different mud types namely bentonite and a natural marine mud (from Beerkanaal, the Port of Rotterdam). A fundamental macroscopic thixotropy model (i.e. Houska) is applied to the experimental data (from both controlled shear rate and controlled shear stress rheometry) to characterize time-dependent rheological properties of these two mud types.
Additionally, typical limitations in determination of thixotropy using rheometer and possible flaws in these measurements are discussed.
Keywords: Mud, Rheology, Rheometry, Thixotropy, Houska Model.