Evaluation of the method of determining unsaturated hydraulic conductivity based on the pore size distribution curve

Unsaturated hydraulic conductivity is key factor governing soil swellings under the effect of frost because it conditions the water transfer driven by the cryo-suction generated by soil freezing. In this study, the unsaturated hydraulic conductivity of a compacted untreated and lime treated silty soil was determined using two methods: 1) calculations based on a capillary tube model involving the pore size distribution curve obtained by the technique of mercury intrusion porosimetry technique, and 2) determination by the instantaneous profile method using the results from isothermal infiltration/drying tests. This enables the two methods to be compared and discussed. Significant difference was observed, showing the limitation of the capillary tube model used in predicting the hydraulic conductivity of soils. However, the calculated hydraulic conductivity-suction curve presents a similar shape to the measured one, suggesting that the main mechanism considered in the model is appropriate.