UNSATURATED HYDRAULIC CONDUCTIVITY OF COMPACTED SAND-KAOLIN MIXTURES

The unsaturated hydraulic conductivity of compacted sand-kaolin mixtur es containing 0, 5, 10, and 30% kaolin (by dry weight) is measured for matric suctions, psi < similar to 6.0 m, The measured unsaturated hyd raulic conductivity (k(measured)) values are compared with predicted u nsaturated hydraulic conductivity (k(predicted)) values using the Broo ks-Corey-Burdine and van Genuchten-Mualem relative hydraulic conductiv ity functions. In general, the accuracy of k(predicted) decreases with an increase in kaolin content or an increase in psi(m). In addition, k(measured) tends to be underpredicted for kaolin contents of 10 and 3 0% at relatively high suctions (1.0 m less than or equal to psi(m) les s than or equal to 6.0 m) and overpredicted for kaolin contents of 0 a nd 5% at relatively low suctions (0.1 m less than or equal to psi(m) < 1.0 m), For a given kaolin content and psi, k(predicted) based on the Brooks-Corey-Burdine function tends to be more accurate than k(predic ted) based on the van Genuchten-Mualem function. Finally, for 1.0 m le ss than or equal to psi(m) less than or equal to 6.0 m, k(predicted) b ased on analysis using the maximum volumetric water content (theta(m)) attained under steady-state flow conditions typically is more accurat e than k(predicted) based on analysis using the saturated volumetric w ater content, theta(s), where theta(m) similar to 84-90% of theta(s) i n this study.