Evolution of Air-Water Interfaces during Soil Water Evaporation

The air-water interfaces occur when air enters the pores and soil becomes desaturated. Surface tension of water stretches and curves the air-water interfaces within the pores and restricted by the pore geometry. The effect of capillarity is stronger as the water content decreases and pore water resides around particle contacts. The air-water interfaces play important role on the heat and mass transfer in porous media such as soil during seepage or evaporation processes, and also greatly affect the interparticle stresses which is relevant to various mechanical properties. This study investigated the evolution of air-water interfaces of soil as the saturation decreases, including the geometrical and topographical features of the interfaces. Glass bead and alluvial sand samples were prepared at various degrees of saturation during the pore water evaporation process. The microstructure and different phases were reconstructed after scanned using micro X-ray CT technology. The calculated total areas and mean curvature distributions of the interfaces and the tortuosity of the pores provide closer thought and deeper understanding on the micro mechanism of soil water evaporation process.