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 the current 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. 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. Compressibility also reduces as molar concentration increases under both saturated and unsaturated conditions with clear reduction in yield suction and stiffness parameter. Microstructural photos confirmed 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 (DDL) and conceptual physics-based capillary and hysteresis models.

中文翻译：

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不同摩尔浓度下土壤保水和收缩特性的滞后

由于环境污染的增加，近年来关于溶质浓度对土壤保水曲线（SWRC）和膨胀土的体积行为的影响的实验室研究受到了广泛关注。但是，大多数研究仅考虑采用润湿或干燥路径，而几乎没有注意液压滞后现象。此外，这些研究集中在检查膨胀土上，只有很少的努力专门用于可塌陷的土壤。因此，本研究的主要目的是系统地研究各种摩尔浓度的人造可塌陷土壤的SWRC和收缩特性。测试是在开发的不饱和自动里程表中进行的，它具有更高的测量精度。结果表明，摩尔浓度对滞后具有明显的线性趋势。与空气进入值相反，解吸率和吸附率均随摩尔浓度的增加而增加。在饱和和不饱和条件下，随着摩尔浓度的增加，可压缩性也降低，屈服吸力和刚度参数明显降低。微观结构照片证实，由于溶质粘土相互作用，与微孔相比，大孔的扩大。根据扩散双层（DDL）理论和基于概念物理学的毛细管和磁滞模型来解释结果。在饱和和不饱和条件下，随着摩尔浓度的增加，可压缩性也降低，屈服吸力和刚度参数明显降低。微观结构照片证实，由于溶质粘土相互作用，与微孔相比，大孔的扩大。根据扩散双层（DDL）理论和基于概念物理学的毛细管和磁滞模型来解释结果。在饱和和不饱和条件下，随着摩尔浓度的增加，可压缩性也降低，屈服吸力和刚度参数明显降低。微观结构照片证实，由于溶质粘土相互作用，与微孔相比，大孔的扩大。根据扩散双层（DDL）理论和基于概念物理学的毛细管和磁滞模型来解释结果。