Hysteresis of soil water retention and shrinkage characteristics for various molar concentrations
Hamed Sadeghi, Hamed Nasiri
Abstract
Laboratory investigation on the influence of solute concentration on the soil water-retention curve (SWRC) and volumetric behaviour of expansive soils has received much attention in recent years due to increasing environmental pollution. However, most studies only considered applying wetting or drying path with almost no attention to hydraulic hysteresis. Furthermore, these studies have focused on examining expansive soils and only marginal effort has been devoted to collapsible soils. Therefore, the main objective of this study is to systematically explore the SWRC and shrinkage characteristics of an artificially made collapsible soil at various molar concentrations. The tests were conducted in a developed unsaturated automatic oedometer with enhanced measuring accuracy. The results reveal the distinct role of molarity on hysteresis with an ascending linear trend. In contrast to the air entry value, both desorption and adsorption rates increase with a rise in molarity, while compressibility reduces under both saturated and unsaturated conditions with clear reduction in yield suction and stiffness parameter. Microstructural photographs confirms the enlargement of macroporosity in contrast to microporosity as a consequence of solute−clay interactions. The results are interpreted in light of the theory of diffuse double layer and conceptual physics-based capillary and hysteresis models.