Rheological Characterization of Fine-Grained Sediments under Steady and Dynamic Conditions

Abstract

The objective of this study is to investigate the steady and dynamic rheological behavior and characteristics of fine-grained sediments. A series of laboratory tests were conducted using an Anton Paar MCR 102 rheometer to investigate the rheological properties of the fine-grained sediments at various water to solid (W/S) ratios. In the steady-state measurement condition, the results indicate that fine-grained sediments are a non-Newtonian viscous fluid, and the presence of yield stress of fine-grained sediments is evident and is influenced by the W/S ratios. For the determination of yield stress, two types of methods were used: by defining the minimum value of shear stress from flow curves experimental data in semilog scale and by modeling the flow curves following different rheological models. From the results obtained, it appears that the Casson model was the best one to characterize the rheological behavior of fine-grained sediments, because of its high coefficient of determination R2 and the lowest mean absolute percentage error, also close to the measured yield stress value. In the dynamic state measurement condition, the loss modulus (G″) is markedly smaller than the elastic modulus (G′), indicating that fine-grained sediments are predominantly elastic (in the range of amplitude and frequencies explored). The complex viscosity (η*) sharply decreases with the frequency increase, but the frequency dependence of the G′ and G″ is rather weak. The G′, G″, η*, and loss factor (tan δ) significantly reduced with the increase of the W/S ratio. In the end, the dynamic rheological properties of fine-grained sediments can be expressed as appropriate functions of the W/S ratios. This study not only provided a guideline for having a better understanding of the rheology of fine-grained sediments but will also provide scientific support for understanding and solving all kinds of natural and manmade activities involving fine-grained sediments, such as dredged sediments handling and transport by pipelines, landslides caused by rainfall or earthquake; generation and movement of mudflows, laying and maintenance of submarine cables and pipelines, and deep-sea mining engineering.