Morphological Changes in Drainage and Imbibition Regions During Water Retention Test

Abstract The mechanisms of drainage and imbibition in pore spaces is crucial for predicting water retention properties and elucidating the unsaturated soil phenomena. In this study, the morphology of the drainage and imbibition regions was analysed to quantitatively evaluate the drainage and imbibition behaviour during the water retention test. The drainage and imbibition regions were extracted from the difference between two sequential images acquired with X-ray micro-computed tomography at each equilibrium point during the drying and wetting processes. Image processing and analysis were performed to investigate the shape complexity of the drainage and imbibition water clusters, which revealed their morphological changes during the water retention test. The drainage clusters were simple shapes during the drying process. During the wetting process, imbibition clusters were complex shapes in a low saturation regime and simple shapes in a high saturation regime.