Pore-scale investigations of partially water-saturated granular soil

Partially water-saturated granular soils are mixtures of soil grains, pore water, and pore air. This study presents methodologies to obtain local quantities, such as porosity, degree of saturation, and pore volume, for partially water-saturated uniform sand at the pore scale. A sand specimen subjected to different water retention states was scanned using X-ray micro computed tomography. The obtained three-dimensional tomographic images were trinarized, i.e. segmented into soil grain, water, and air phases. The trinarized volumes were divided into Voronoi cells containing individual pores, and the volume and degree of saturation for the pores were calculated. Alternatively, the porosity and degree of saturation were quantified for cubical local subsets arranged regularly in the trinarized volumes. Pore characteristics and local water retention behavior are discussed using the results of these two investigations.