Influence of soil microstructure on disintegration characteristics of a compacted clayey soil under drying

Under heavy rainfall and fluctuating groundwater levels, soils are highly susceptible to disintegration, which may trigger a range of engineering and geological hazards. This study investigates the influence of soil microstructure, shaped by compaction water content and subsequent drying, on the disintegration behavior of compacted clayey soil. Disintegration tests were performed on samples compacted at varying water contents (12.5%-20.5%) and subsequently dried to target water contents. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used to characterize pore structure and microstructural changes before and after drying. Results show that compaction water content plays a critical role in shaping the soil microstructure, thereby influencing both its disintegration behavior and response to drying. At lower compaction water contents, aggregated structures with bimodal pore distributions are formed, whereas higher compaction water contents lead to dispersed structures dominated by micropores. These structural differences result in distinct disintegration characteristics: aggregated soils exhibit rapid, complete, and granular disintegration, while dispersed soils display gradual, surface-limited, and incomplete disintegration. Upon drying, aggregated structures undergo overall densification and pore collapse, strengthening the soil matrix and suppressing disintegration. In contrast, dispersed structures tend to develop fissures and larger inter-particle voids during drying, weakening the structure and enhancing disintegration. This study establishes a direct “compaction state-microstructure-disintegration” relationship, contributing to understanding of how microstructural evolution under varying compaction and drying conditions governs disintegration behavior. The study offers practical implications for the design and maintenance of compacted soil structures, particularly under drying-wetting cycles in arid and semi-arid climatic conditions.