The effect of grain size on the viscosity and yield stress of fine-grained sediments
- 322 Downloads
In debris flow modelling, the viscosity and yield stress of fine-grained sediments should be determined in order to better characterize sediment flow. In particular, it is important to understand the effect of grain size on the rheology of fine-grained sediments associated with yielding. When looking at the relationship between shear stress and shear rate before yielding, a high-viscosity zone (called pseudo-Newtonian viscosity) towards the apparent yield stress exists. After yielding, plastic viscosity (called Bingham viscosity) governs the flow. To examine the effect of grain size on the rheological characteristics of fine-grained sediments, clay-rich materials (from the Adriatic Sea, Italy; Cambridge Fjord, Canada; and the Mediterranean Sea, Spain), silt-rich debris flow materials (from La Valette, France) and silt-rich materials (iron tailings from Canada) were compared. Rheological characteristics were examined using a modified Bingham model. The materials examined, including the Canadian inorganic and sensitive clays, exhibit typical shear thinning behavior and strong thixotropy. In the relationships between the liquidity index and rheological values (viscosity and apparent yield stress), the effect of grain size on viscosity and yield stress is significant at a given liquidity index. The viscosity and yield stress of debris flow materials are higher than those of low-activity clays at the same liquid state. However the viscosity and yield stress of the tailings, which are mainly composed of silt-sized particles, are slightly lower than those of low-activity clays.
KeywordsDebris Flow Viscosity Yield Stress Grain Size Fine-Grained Sediments
Unable to display preview. Download preview PDF.
- Bagnold RA (1954) Experiments on a gravity-free dispersion of large solid spheres in a Newtonian fluid under shear. Proceedings of the Royal Society, 6 August 1954, London, UK. Vol. 225. pp. 49–63. DOI: 10.1098/rspa.1954.0186Google Scholar
- Coussot P (2007) The mechanics of yield stress fluids: similarities, specificities and open questions. 16th Australasian Fluid Mechanics Conference, Crown Plaza, Gold Coast, Australia. pp. 54–58.Google Scholar
- Iverson RM, Vallance JW (2001) New views of granular mass flows. Geological society of America 29: 115–118. DOI: 10.1130/0091-7613(2001)029<0115:NVOGMF>2.0.CO;2Google Scholar
- Jeong SW (2006). Influence of physico-chemical characteristics of fine-grained sediments on their rheological behavior. PhD Thesis, Laval University, Quebec, Canada.Google Scholar
- Locat J (1997) Normalized rheological behaviour of fine muds and their flow properties in a pseudoplastic regime. Proceedings of the 1st International Conference on Debris-Flow Hazards Mitigation, San Francisco. ASCE, New York. pp 260–269.Google Scholar
- Malet JP, Remaître A, Maquaire O, et al. (2003) Flow susceptibility of heterogeneous marly formations. Implications for torrent hazard control in the Barcelonnette basin (Alpes-de-Haute-Provence, France). In: Rickenmann D and Chen CL (Eds.), Proceedings of the 3rd International Conference on Debris-Flow Hazards Mitigation, Millpress, Rotterdam, The Netherlands. pp. 351–362.Google Scholar
- Mitchell JK (1993) Fundamentals of soil behavior. 2nd ed. New York, John Wiley & Sons, Inc. pp 450.Google Scholar