Hydro-mechanical behaviour of Nanyang expansive soil during the wetting–drying cycles

Expansive soils, characterized as typical problematic soils, present significant challenges to geotechnical engineering due to their distinctive hydraulic-mechanical behaviour, particularly under varying environmental conditions. This study established a comprehensive testing framework to examine the hydraulic-mechanical properties of Nanyang expansive soil. The framework systematically integrated key properties during moisture variations, including swelling tests, shrinkage tests, water retention curve measurements on both the drying and wetting paths, and strength–permeability evaluations under wetting–drying (W–D) cycles. The results showed that both void ratio and axial strain exhibited a strong positive correlation with water content. Notably, specimens with lower initial water content presented more pronounced expansion, whereas those with higher initial water content underwent greater shrinkage and developed significant anisotropic deformation during drying. Repeated W–D cycles led to crack development, resulting in a significant reduction in shear strength and a notable increase in permeability. These findings highlighted the coupled deformation and hydraulic behaviour of expansive soils under cyclic climatic conditions, providing valuable insights into their long-term deterioration. The results support the development of more reliable design and maintenance strategies for geotechnical systems in high-risk expansive soil regions.