Predicting Soil Hydraulic Properties from Particle Size Distribution and X-Ray Tomography.

Knowledge about soil hydraulics properties such as water retention characteristic and the hydraulic conductivity curves are fundamental for water flow and solute transport modeling in the vadose zone. However, the characterization of these properties is very time-consuming and requires many sample manipulations. Today, advances in the field of tomography imagery allow the characterization of a number of soil hydraulic properties (Wildenschilds and Sheppard, 2013). Indeed the use of μCT-scan allows the characterization of the porous media at the pores scale, giving information about the pore size distribution and the pore network connectivity itself. However, most of the time the use of the μCT-scan is limited to very small sample, which is inappropriate to study a representative, volume of soil. Therefore, the main objective of this work is to propose a framework to predict soil hydraulic properties from the combination of particle size distribution and X-ray tomography of a porous media. For that a 1m-high sandy soil cylinder was characterized with a medical CT-scan with a 100 µm voxel. Also the water retention curve and the hydraulic conductivity were analyzed during drainage and recharge with instantaneous profile method. Moreover, the soil particle size distribution was obtained within a LA950v2 Laser Particle Size Analyzer (Horiba). The soil hydraulic properties obtained from the framework application showed a very good agreement with those obtained with current soil physics measurements. The development of such a method, which is able to predict the soil hydraulic properties within the combination of particle size distribution and X-ray tomography is of major concern for water management and soil water dynamic modeling.

References:

Wildenschild, D. and A.P. Sheppard. 2013. X-ray imaging and analysis techniques for quantifying pore-scale structure and processes in subsurface porous medium systems. Advances in Water Resources 51: 217-246. doi:http://dx.doi.org/10.1016/j.advwatres.2012.07.018.