The effects of clay minerals on flocculation process of cohesive sediment in estuarine areas: a review of floc structure and floc strength

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Naiyu Zhang, Jingjing Zhou, Jie Wang

Friday 3 july 2015

12:00 - 12:15h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling

Parallel session: 15B. Sediment - Transport

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The orthokinetic flocculation of cohesive sediment is prevalent and much of the suspended particulate matter (such as the transport of contaminant, mouth bar) exists in the form of flocs. Therefore, predicting flocculation process is vital. Flocculation is a dynamic process which can be included as: particle collision-cohesion-breakage-reaggregation. Primarily, floc structure and floc strength is an issue throughout the whole dynamic process. For a given shear rate, floc strength is an indication of floc structure. Both floc strength and floc structure are the combination results of sediment composition and hydrodynamic conditions around. The correlation of mineralogy and floc strength and floc structure under turbulence condition is, therefore, worth further investigation. Currently, the investigation of synergistic effect of different clay minerals on flocculation is rare. In this paper, the significance of mineralogy on flocculation is analyzed. The current theoretical understanding and experimental study of floc structure and floc strength is reviewed. An analysis of different techniques for measuring floc structure and floc strength is also made. The usage of powerful digital and CCD cameras and comprehensive image analysis is a relatively ideal method. Generally, the experimental study of floc strength and floc structure is conducted by measuring floc size and mass fractal dimensions respectively, and then floc strength and floc structure can be calculated. These calculation methods are also listed. Finally, after summarization,A proposal for the further experimental study in terms of synergistic effect of different clay minerals on floc strength and floc structure is presented. This can be done by laboratory experiments to obtain its general trend and data processing to establish a quantitative analysis of the influence of clay minerals on floc strength and floc structure.