Effect of Clay Content on Suction and Swelling Behavior in Unsaturated Soils: Insights from Water Retention and Oedometric Testing

The swelling behavior of clay soils remains a significant concern in geotechnical engineering due to its potential to cause significant structural damage and deformation. Understanding the mechanisms behind this behavior is critical, with suction identified as the primary driver of volume change in unsaturated expansive clays. This study focuses on two soil mixtures with different clay contents, examining and comparing their swelling responses through oedometric testing. In parallel, water retention curves (WRCs) were established for both total and matric suction to analyze moisture retention characteristics. The results demonstrate that increased clay content intensifies both suction and swelling behavior, with a notable rise in the difference between total and matric suction, indicating an enhanced osmotic effect. The MK model was applied to interpret these curves, though its prediction showed some limitations, suggesting that while it is useful for some types of soils, it may not fully capture the complexity introduced by varying swelling clay content. The integration of swelling measurements with suction analysis and modeling underscores the crucial role of suction in predicting and managing the behavior of expansive soils.