Unsaturated Hydraulic Conductivity of Compacted Sand-Kaolin Mixtures

Abstract
The unsaturated hydraulic conductivity of compacted sand-kaolin mixtures containing 0, 5, 10, and 30 kaolin (by dry weight) is measured for matric suctions, ψm<∼6.0 m. The measured unsaturated hydraulic conductivity (kmeasured) values are compared with predicted unsaturated hydraulic conductivity (kpredicted) values using the Brooks-Corey-Burdine and van Genuchten-Mualem relative hydraulic conductivity functions. In general, the accuracy of kpredicted decreases with an increase in kaolin content or an increase in ψm. In addition, kmeasured tends to be underpredicted for kaolin contents of 10 and 30 at relatively high suctions (1.0 m ≤ψm≤ 6.0 m) and overpredicted for kaolin contents of 0 and 5 at relatively low suctions (0.1 m ≤ψm< 1.0 m). For a given kaolin content and ψm, kpredicted based on the Brooks-Corey-Burdine function tends to be more accurate than kpredicted based on the van Genuchten-Mualem function. Finally, for 1.0 m ≤ψm≤ 6.0 m, kpredicted based on analysis using the maximum volumetric water content (θm) attained under steady-state flow conditions typically is more accurate than kpredicted based on analysis using the saturated volumetric water content, θs, where θm∼ 84–90 of θs in this study.