Characterization of Soil Hydraulic Properties Heterogeneity in Sandy Soil By Tomodensitometric Analysis and Particle Size Distribution.

Knowledge of soil hydraulic properties such as water retention and hydraulic conductivity are essential for modelling water flow and contaminant transport in soils. However, characterization of these properties requires many technical operations that are very costly and time consuming. Tomodensitometric analysis offers a cost-effective and fast methodological approach to analyze a number of soil hydraulic properties. Indeed, micro scanning can be used to characterize porous media at high spatial resolution and to obtain pore size distribution and pore network. However, the use of micro scanning has limits on sample size making unsuitable the study of a representative volume of a specific process described by a macroscopic model. The main objective of this work was to develop a framework to predict equivalent soil hydraulic properties and to analyze the heterogeneity of soil hydraulic properties using a combination of X-ray tomographic imaging and particle size analysis. A sandy soil sample was characterized with a medical CT scan at a resolution of 100 µm for a voxel. Water retention and hydraulic conductivity curves were derived using the instantaneous profile method for sorption and desorption curves. Moreover, the soil particle size distribution was obtained within a LA950v2 Laser Particle Size Analyzer (Horiba). Results showed good prediction of equivalent soil hydraulic properties. The development of this novel framework has provided an opportunity to study the heterogeneity of soil hydraulic properties of a porous media at a fine resolution (100 µm) on soil column of 1 m of length (representing soil profile scale).