Expansive soils are highly reactive and the hydro-mechanical behavior is sensitive to the pore solution chemistry. In this paper, the role of physicochemical effect on the shrinkage-swelling behavior of expansive soil in a drying and wetting circle was investigated in experimental and theoretical studies. The soil water characteristic curves (SWCCs) and soil shrinkage curves (SSCs) were obtained on the samples with different NaCl concentrations. In terms of matric suction, the experimental results of SWRCs represented by gravitational water content or degree of saturation exhibited different trends with the change of salt content, due to the large role of pore water chemistry on the deformation. Therefore, only SWRCs obtained by traditional methods without deformation measured is not enough for simulating hydro-mechanical behavior of expansive soils. During drying-wetting process, the shrinkage-swelling behavior was actually a process of compression governed predominantly by the development of effective stress with the variation of water content instead of matric suction. From mechanical perspective, the intergranular stress was introduced to represent the compression behavior, which can consider osmosis, capillary and adsorption effects into a unified formula. Based on the theoretical studies, the intergranular stress can describe the elastic-plastic deformation in the capillary regime and the elastic deformation in the adsorption regime. It is worthy to note that the threshold value distinguishing the capillary and adsorption in the compression curve based on Casagrande method is consistent with the value obtained from independent SWRCs at different compactness. These results validated the capability of intergranular stress to describe the chemico-mechanical coupling behavior better than the traditional Bishop’s type effective stress, especially in the dry end. 

膨胀土