Dependence of anisotropy on saturation in a stratified sand

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Abstract
A laboratory experiment was performed to investigate the movement of water infiltrating from a point source into a porous medium comprised of alternating layers of fine and coarse sand packed in a clear plastic tank. The purpose of the experiment is to demonstrate whether the effective anisotropy of stratified materials is dependent upon saturation. The noncolinearity of the specific discharge and hydraulic head gradient directions is used as a measure of anisotropy. Dyes were used to map the specific discharge direction and tensiometers were used to characterize the hydraulic gradient field under unsaturated, steady state conditions. The results indicate a divergence between the direction of the specific discharge and gradient which increases as the pressure head decreases. Anisotropy determined from the experiment exceeds that calculated from the hydraulic conductivities of the individual materials.