Velocity-Gradient Relationships for Steady-State Unsaturated Flow of Water in Nonswelling Artificial Soils
Olson, T. C. | Swartzendruber, D.
The relationship between flow velocity and hydraulic gradient was studied for steady-state unsaturated flow of water in horizontal columns of two nonswelling porous media, one a mixture of sand, ground silica, and kaolinite, and the other a mixture of sand and ground silica only. The flowing water contained 0.1% phenol to inhibit bacteria. Soil-moisture tension was measured with three tensiometers positioned within the soil column. Gradients at different velocities could be determined at a single location. Tension changes were always from low to high, to eliminate hysteresis effects. This required the use of a graphical analysis to calculate corresponding values of velocity and gradient at a given constant tension. In general, essential proportionality between flow velocity and tension gradient at given tension was found for both materials. Very slight greater-than-proportional tendencies were present in the sand-silica-kaolinite mixture, but were not consistently related to tension. In the sand-silica mixture a less-than-proportional flow response was observed at low and intermediate tensions, but became proportional as the tension increased. Minimal pore-volume saturations achieved were 0.74 for the sand-silica-kaolinite, and 0.65 for the sand-silica.Show more [+] Less [-]