2008 Volume 108 Pages 11-17
Some new field techniques for measuring unsaturated soil hydraulic properties by using soil water content measured from dielectric properties of unsaturated soils are proposed. Firstly in-situ permeability tests for unsaturated soils are developed. The constant head infiltration test and the gravity drainage test were performed continuously. The transient soil water content data during these tests were measured by a portable soil moisture device. The vertical soil moisture profiles during the drainage test were used to determine the unsaturated hydraulic conductivity. The inverse solution of unsaturated soil hydraulic functions was applied to independently measured transient water content for wetting and drying process to consider hysteresis phenomenon of unsaturated soil hydraulic properties. Secondly surface ground-penetrating radar (GPR) system is employed to estimate the average soil water content profiles in the survey region as a function of the dielectric constant measured by electromagnetic wave velocities. GPR offers a simple and nondestructive approach for in-situ determination of soil water content. The utilities of proposed methods are demonstrated by using field experimental data for unsaturated dune sands.
