Journal of the Japanese Society of Soil Physics
Online ISSN : 2435-2497
Print ISSN : 0387-6012
Settling velocity of high-density clay suspension and effects of vertical channel formation
Katsuya NAKAISHISetsuo OOI
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2014 Volume 127 Pages 11-18

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Abstract

The effects of channel formation on settling ve-locity have not yet been clarified for high-density clay sus-pensions. In this study, we examined the effects of ver-tical channel formation conditions on channel shape and channel flow rate by a method where artificial bubbles were passed upward through a column containing a sus-pension of kaolinite. Specifically, settling velocity, chan-nel diameter, and channel number density were measured by photographic methods. These data were used to cal-culate channel flow rates, which were then compared with the values expected for Hagen-Poiseuille flow. At a high solid concentration (1.1 % 〜4.0 % by volume), vertical channels did not form unless artificial bubbles were ap-plied, because the suspension became highly viscous. The number of channels formed by applying bubbles decreased sharply with increasing solid concentration, whereas verti-cal channel diameter increased with increasing solid con-centration. As a result, there was a peak settling velocity at a solid concentration of 2.2 % by volume. Under con-ditions without structural force, the relation was examined between measured diameter and flow rate diameter (i.e., the mean of diameter to the 4th power) calculated from set-tling velocity using Darcy’s law and the Hagen-Poiseuille equation. The calculated diameter of channels formed by artificial bubbles agreed well with the measured diameter at low solid concentration (< 2.2 %), but was lower than the measured diameter at high solid concentration (> 2.2 %). These results show the importance of structural force in high-density clay suspensions.

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© 2014 Japanese Society of Soil Physics
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