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Permanent link (DOI): https://doi.org/10.7939/R31D6K

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Fundamentals of Segregation Open Access

Descriptions

Other title
Subject/Keyword
Segregation, Rheology, Yield Stress, Oil Sands Tailings
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Mihiretu, Yetimgeta
Supervisor and department
Chalaturnyk, Rick (Civil and Environmental Engineering)
Examining committee member and department
McCaffrey, William (Chemical and Materials Engineering)
Yanful, Ernest (External Examiner, University of Western Ontario)
Driver, Robert (Civil and Environmental Engineering)
Chalaturnyk, Rick (CIvil and Environmental Engineering)
Sego, Dave (Civil and Environmental Engineering)
Department
Department of Civil and Environmental Engineering
Specialization

Date accepted
2009-10-08T16:37:42Z
Graduation date
2009-11
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
A common challenge during deposition of slurries is segregation as large particles settle through the matrix of fines and water. Whether segregation occurs or not depends on the grain size distribution of the solids, the void ratio or solids content and the rheological properties of the fines-water matrix. The rheological characterization of slurry composed of different grain sizes and varying water chemistry was investigated. The vane yield stress was used to characterize different slurries composed of clay, silt and sand materials. Semi-empirical fractal theory showed good agreement with experimental data for fine slurry. Comparison of yield stress at same concentration but different composition showed a decreasing trend as the composition of either silt or sand material increases. The pore-water effect was studied for representative kaolinite slurry. The yield stress was insensitive for pH values in the acidic and neutral range, while in the basic range it showed significant response depending upon the type of the chemical used to achieve the pH: Ca(OH)2 and NaOH. A modified segmented standpipe was designed and used in a series of experiments to determine concentration profiles during the sedimentation processes. Analyses of the solid content profiles and sand content profiles in the standpipes indicated a capture of sand particles which could be correlated to the yield stress of the fines matrix. Theoretical calculations, however, showed over-prediction of the captured sand size. A correction factor of about 0.2 was applied. Flume test on a high solid content slurries showed that the dynamic segregation is governed by all the factors governing the static case. Beaching profile shapes were not a necessary indication of segregating and non-segregating type of slurries. Modified version plastic theory for flow slides was used to characterise profile shape. Computational fluid dynamics approaches based on kinetic theory and bi-viscous model analysis were implemented and showed a reasonable capability in modelling segregation when compared with experimental results. A statistical formulation for segregation index, SI, was proposed. The index accounts for variation in depth of samples. Finally recommendations for future research are proposed based on the observations and findings made from the study.
Language
English
DOI
doi:10.7939/R31D6K
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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