Author(s): Xiaoteng Shen; Mingze Lin; Qilong Bi
Linked Author(s):
Keywords: Viscosity; Cohesive sediment; Solid volume concentration; Laboratory experiment; Empirical model
Abstract: 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 (1906) 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, the developed model was coupled with a hydrodynamic model to simulate a one-dimensional dam failure. 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.
Year: 2024