Review Notes on Cohesive Sediment Erosionby Ashish J. Mehta, Univ of Florida, Gainesville, United States,
Abstract: Comments are made on issues related to surface and mass erosion phenomena associated with cohesive sediment beds, and the entrainment of fluid mud. The rate process theory is recapped to highlight the dependence of surface erosion rate on the excess bed shear stress and the absolute temperature. A qualitative argument is presented to emphasize that standard soil strength measuring devices are unsuitable for measuring the bed erosion shear strength which, in freshly deposited beds, is influenced both by consolidation and gelling. By introducing the concept of a 'stirred' near-bed layer it is argued that erosion can be viewed either as a process involving solely upward entrainment of broken bed aggregates, or as an exchange process involving simultaneous entrainment and settling. Some experimental evidence is presented to show that mass erosion can occur at comparatively low applied stresses over weak beds. Finally, it is suggested that the entrainment of fluid mud can not be modeled in the same way as bed erosion.
Subject Headings: Erosion | Entrainment | Shear stress | Bed materials | Shear strength | Fluidized bed technology | Mud | Soil strength
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