Determination of the unsaturated hydraulic conductivity of clayey soil columns using Magnetic Resonance Imaging (MRI)

Abstract

In some conditions, soils can be simultaneously submitted to thermal and hydraulic changes under which their unsaturated hydraulic conductivity (ku ) can evolve. The determination of the changes with time of water content profiles inside soil columns submitted to 1D soaking or drying is a possible approach to calculate ku based on the instantaneous profile method, but it is a complex task. In this study, a Magnetic Resonance Imaging (MRI) method named Single Point Imaging was used to monitor changes in water content. First, a calibration curve relating the MRI signal to the water content of samples prepared at various water contents and densities was determined. Then the method was applied on clayey sample (argillite) submitted to two drying tests for at least 4 days at 20 and 40°C. The imposed hygrometry was 33%. Finally, the Instantaneous Profile Method was used to determine ku values from water content profiles. This method was successful in recording the impact of the heating on the drying kinetics.