94 / 2024-01-11 14:07:36

Rheological Characteristics of Sediment Suspensions: Experimental Investigations and Empirical Modelling

Rheological behavior,Non-Newtonian fluid,laboratory test

Cohesive sediments are commonly found in rivers, estuaries, and wastewater treatment facilities. To understand their behavior close to the bed, it is crucial to study the rheology, focusing on the viscosity of highly concentrated suspensions and their resistance to deformation. In this study, a rotational viscometer was used to explore how relative viscosities (ηr) relate to volumetric concentrations (ϕ) for different sediment types. The results indicate a significant underestimation by the conventional Einstein’s formula for diluted sand when applied to highly concentrated suspensions of sediment. For pure silts and non-cohesive quartz, the relative viscosity demonstrated a gradual linear increase with volumetric concentration. In contrast, clays exhibited an initial exponential rise, eventually reaching a plateau. Notably, kaolinite, montmorillonite, and bentonite show a more rapid increase in viscosity compared to chlorite and illite. 

In addition, a modified viscosity model was proposed to simulate the ηr ~ ϕ relationship for the suspensions, which agreed reasonably well with observations. Furthermore, viscosity experiments conducted with field mud from also validated the proposed model, showing a good accuracy in fitting the results. The developed model was coupled with TELEMAC-2D, a hydrodynamic open-source model, to simulate the deposition of a thickened tailings slurry. The simulation results demonstrated the applicability of the developed model in predicting the sediment transport and deposition processes in practical engineering scenarios.

Further studies should pay more attention to the impact of flow properties, especially for non-Newtonian fluids, and their applications in large-scale modelling. This study, overall, offers valuable insights into the rheological characteristics of suspended sediments, essential for understanding sediment transport and deposition in both natural and engineered systems.