ABSTRACT
Dispersion coefficient was determined from the best fitting of one-dimensional advection-dispersion model to laboratory experiments done by a column with 5cm diameter and 30cm length. Suction is applied at the bottom to get rid of the end effect and to keep a constant water saturation throughout the column. The Toyoura sand was packed and sodium chloride solution is supplied with steady state flow condition. The experiments showed that dispersion coefficient increases dependency on decrease of water saturation and linear relationship exists between dispersion coefficient and average pore water velocity. The study highlights linear increase of dispersivity, which is defined by dispersion coefficient divided by average pore water velocity, as water saturation decreases. Discussions were placed on the comparisons with dispersivity of the glass beads and the applications to a numerical analysis for transient movement of chemical constituent through variably saturated sand.
