Water Retention Behaviour Explored by X-Ray CT Analysis

Abstract

This study aims to experimentally characterise the link between partial water saturation and suction in a sand sample at the micro scale. The paper presents the first results of an experimental study in which high resolution (7.5μm/px) X-ray tomography has been performed on a small (10×10mm) cylindrical sample of Hostun HN31 sand at several different levels of imposed suction. A specialised cell allowing X-ray scanning as well as fine control of suction (imposed both by negative water pressure as well as by positive air pressure) has been developed for this study and is described herein. The 3D images resulting from X-ray tomography are treated in order to define each voxel in the image as either air, water or grain. From these “trinarised” 3D images, local and global values of porosity and degree of saturation are then measured. This method enables the study of water retention behaviour of sand at the grain scale, all the while allowing characterisation of water retention in the sample as a whole.