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No description available.

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. / Geotechnical Engineering

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This research is a follow up to preliminary studies reported by Beier and Sego (2008) and the objective is to investigate laboratory scale dewatering of oil sands total tailings using cross flow filtration technology. A laboratory experiment was setup in Oil Sands Tailings Research Facility and tests were carried out under different operational conditions using different tailings. The experiments showed clean filtrate water generated under all test conditions. Coarser tailings and higher filter pipe porosity resulted in greater filtrate flux rate. The effect of slurry velocity, residual bitumen, and transmembrane pressure on cross flow filtration performance was also evaluated. A dimensional analysis was developed using the laboratory tests to establish the relationships between measured parameters and to assist and guide future experimental programs. / Geotechnical Engineering

This research is an experimental, field and numerical study of the sedimentation and consolidation of in-line thickened oil sands fine tailings. In-line thickening is a process that adds flocculant and coagulant into a modified tailings pipeline in a multi stage fashion to improve the dewatering behaviour of oil sands fine tailings cyclone overflow. The parent untreated cyclone overflow, in-line thickened tailings and sheared in-line thickened tailings were investigated in the laboratory. In-line thickened tailings were produced in the laboratory using the same process as in the field project and sheared in-line thickened tailings were prepared by shearing the thickened tailings with a specified shearing effort to simulate tailings transportation. A combination of hindered sedimentation tests, compressibility standpipe tests and large strain consolidation tests with vane shear tests was then used to capture a full range of sedimentation, consolidation and shear strength characteristics for these materials. Results show that the in-line thickening process significantly improves hydraulic conductivity and undrained shear strength of the fine tails. Shearing damages some of the floc structure but does not cause the material to fully return to the original state of the cyclone overflow. The laboratory data of the in-line thickened tailings was compared with field performance at two in-line thickened tailings pilot scale ponds and with a validation standpipe test by utilizing a developed finite strain consolidation model. Good agreements were obtained between the field performance, the laboratory test results and the validation standpipe test. These good agreements confirmed the validity of the laboratory determined geotechnical parameters and of the developed numerical model and indicated that it is possible to model large scale field performance with small scale laboratory tests. Finally, composite tailings was made from the in-line thickened tailings and was found to have a similar segregation boundary to that of gypsum treated composite tailings made with mature fine tailings but had a much higher hydraulic conductivity and shear strength which were inherited from the flocculated fines. / Geotechnical Engineering

No description available.

No description available.

No description available.