Chapters authored
Rheology of Mud: An Overview for Ports and Waterways Applications
Mud, a cohesive material, consists of water, clay minerals, sand, silt and small quantities of organic matter (i.e., biopolymers). Amongst the different mud layers formed by human or natural activities, the fluid mud layer found on top of all the others is quite important from navigational point of view in ports and waterways. Rheological properties of fluid mud layers play an important role in navigation through fluid mud and in fluid mud transport. However, the rheological properties of mud are known to vary as a function of sampling location within a port, sampling depth and sampling location across the globe. Therefore, this variability in rheological fingerprint of mud requires a detailed and systematic analysis. This chapter presents two different sampling techniques and the measured rheological properties of mud, obtained from laboratory experiments. The six protocols used to measure the yield stresses are detailed and compared. Furthermore, the empirical or semi-empirical models that are commonly used to fit rheological experimental data of such systems are presented. The influence of different factors such as density and organic matter content on the rheological behavior of mud is discussed. The fluidic yield stress of mud samples was observed to vary from 0.2 Pa to 500 Pa as a function of density and organic matter content.
Part of the book: Sediment Transport
Flocculation in Estuaries: Modeling, Laboratory and In-situ Studies
Modelling the flocculation of particles in a natural environment like an estuary is a challenging task owing to the complex particle-particle and particle-hydrodynamic interactions involved. In this chapter a summary is given of recent laboratory and in-situ studies regarding flocculation. A flocculation model is presented and the way to implement it in an existing sediment transport model is discussed. The model ought to be parametrized, which can be done by performing laboratory experiments which are reviewed. It is found, both from laboratory and in-situ studies, that flocculation between mineral sediment and organic matter is the dominant form of flocculation in estuarine systems. Mineral sediment in the water column is < 20 μm in size and its settling velocity is in the range [0–0.5] mm/s. Flocs can then be categorized in two types: flocs of size [20–200] μm and flocs of size > 200 μm. The origin of these two types is discussed. The two types of flocs are found at different positions in the water column and both have settling velocities in the range [0.5–10] mm/s.
Part of the book: Sediment Transport