Determining the Soil Water Characteristic Curve and Interfacial Contact Angle from Microstructural Analysis of X-Ray CT Images

Abstract

The complex behavior of unsaturated soils can be partly attributed to the co-existence of networks of liquid bridges and saturated pockets in the soil void space. Past studies have examined how the water bridges and pockets behave when suction changes in soils. The study described here uses microfocused industrial X-ray computed tomography (X-ray μCT), to closely examine unsaturated geomaterials. In this study, an unsaturated glass bead sample was scanned in a suction-controlled setup. Images of the interphase microstructure were processed using image processing techniques. Water-air and solid-water interfaces were distinctively identified using phase-based segmentation. The soil water characteristic curve (SWCC) of the tested granular specimen was quantified by processing microstructural images that were obtained with X-ray computed tomography (CT) scanning. Values of interfacial contact angle were measured on orthogonally projected planes, and the associated results are presented and discussed.