Browsing by Author "Neill, R I G"

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    The rheology and flow behaviour of high concentration mineral slurries
    (1988) Neill, R I G; Lazarus, JH
    The rheology and flow behaviour of high concentration backfill tailings are investigated using a modified Balance Beam Tube Viscometer. The viscometer is capable of producing reliable data using a computer based data acquisition system and three different tube diameters. The aim of this research is to determine the rheology of backfill tailings in order to predict friction head losses. The backfill tailings were prepared into four different particle size distributions each with a different maximum particle size. Each particle size distribution was tested over a range of high concentrations in the viscometer. The rheology of the lower concentration backfill tailings was successfully characterized using the yield-pseudoplastic model. It has been found that at high concentrations rheological characterization is impossible because the laminar flow region of the pseudo-shear diagram varies with tube diameter. This anomalous behaviour in the form of diameter dependence has been recorded in the literature. The results of high concentration tests on backfill tailings are investigated using the following theories to establish and account for the cause of the anomalous behaviour: Effective slip analysis - corrects the measured data for effective slip. Dense-Phase Model - based on the sliding friction between solid particles and the tube wall. Wall Effect - based on a reduction of in situ concentration due to a wall effect. Boundary-Layer Effect - corrects for the effect of a boundary-layer of liquid at the wall. Modified Friction Factors - takes into account the hydrodynamic lubrication between the solid particles and the tube wall. The existence of a thin layer of liquid at the wall is credible but not yet proven. The anomalous behaviour is linked to this layer. However a suitable method for correcting the measured data has not yet been established.