Flux-Gradient Relationships for Saturated Flow of Water through Mixtures of Sand, Silt, and Clay
Russell, D. A. | Swartzendruber, D.
Water flux was studied as a function of hydraulic gradient for water-saturated mixtures of sand, silt, kaolinite, illite, and bentonite. Flow rates were measured in sensitive capillary-tube flowmeters containing differential manometers, such manometers also being used to measure gradients across the permeameters. Measurements were relatively rapid and were obtained for a series of increasing gradients followed immediately by repetition of alternate points in the direction of decreasing gradients. The method eliminated errors arising from time changes in hydraulic conductivity, evaporation loss at the flow outlet, and bubble movement in small-bore capillary tubes. Nonswelling mixtures (sand, silt, kaolinite, and illite) generally exhibited good Darcian proportionality between flux and gradient, except for two less-than-proportional responses, one of which could be accounted for by fine-particle migration. Swelling mixtures (sand, silt, and bentonite) yielded nonproportional flux-gradient curves of a generally sigmoidal shape.Show more [+] Less [-]