Hydraulic conductivity is an important parameter in the design of geotechnical structures such as earth dam, floor construction, retaining walls and environmental structures. In unsaturated soils, hydraulic conductivity is a function of moisture content and soil water suction i.e. soil moisture characteristic curve. In this study, the values of unsaturated hydraulic conductivity in two soil types (Ramjerdi and Molasadra core dam series) at 5 different compactions using Gardner method were measured. Then, the unsaturated hydraulic conductivity was estimated by different models using the soil moisture characteristic curve and was compared with measured values. The results showed that Fredlund and Xing models predict the soil moisture characteristic curves more accurately compared with van Genuchten model. For Ramjerdi soil series and up to nearly 0.25 volumetric water content, (VGM) and (FM) models indicated a good estimation for unsaturated soil conductivity. Also, for Molasadra core dam none of the models resulted in acceptable estimations for unsaturated hydraulic conductivity.

Keywords: Soil moisture characteristic curve, Unsaturated hydraulic conductivity, Compacted soils

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