Investigating the effect of compaction states on desiccation cracking characteristics of lateritic soil subjected to drying-wetting cycles

Abstract

Lateritic earth dams were subjected to drying-wetting (D-W) cycles, which induced desiccation cracks and threatened its safety. This study examined the cracking behavior and micro-scale mechanisms of lateritic soil under varying compaction states and five D-W cycles. Desiccation cracks were quantified using image processing technique, while microstructure was examined by the mercury intrusion porosimetry and scanning electron microscopy tests. The results showed that the surface crack ratio R_sc decreased as compaction water content increased from the dry to the wet side, as reduced macro-pore volume and connectivity inhabited crack formation and penetration. With increasing dry density ρ_d, R_sc increased for the lateritic soil in present study but decreased for the pure clay soils reported previously, which was attributed to their distinct soil fabrics — a coarse–coarse contact dominated fabric for the lateritic soil and a fine–fine contact dominated fabric for the pure clay soils. Increasing ρ_d reduced permeability and intensified water content gradient between the specimen surface and bottom, thereby increasing tensile stress in both fabrics. Meanwhile, increasing ρ_d slightly increased tensile strength for the former fabric but significantly increased it for the latter, resulting in opposite cracking trends. With increasing D-W cycles, cracks underwent three stages: initiation (N = 0–1), propagation (N = 1–3), and stabilization (N = 3–5). These cracks acted as preferential pathways for deep soil evaporation and rainwater infiltration, threatening earth dam stability. These findings support stability assessment of lateritic earth dams under reservoir fluctuations.