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In this study, the intact Nanning stiff clay were subjected to cyclic wetting–drying under different axial constrain conditions. Experimental results showed that specimen presented vertical stress-dependent axial strain under one-dimensional condition, and gave varying axial stress responses under limited-axial swelling condition. At the first wetting stage, the swelling pressure extrapolated from the swelling strain–vertical stress relationship was found well comparable to that measured on the intact specimen hydrated under constant-volume condition. The proceeding wetting–drying cycles caused structural deterioration of the intact specimens, which differed under different constraint conditions, thus giving rise to different swelling behaviour of the soil. Under one-dimensional condition, the swelling deformation directly destroyed the diagenetic structure of the natural expansive stiff clay. Increasing the vertical stress helps prohibiting such destructive effect. While under limited-axial swelling condition, the specimen swelled to develop varying axial stress in response to hydration during each wetting–drying cycle. More interestingly, the developed axial stress presented a considerable decrease after it remained comparatively stable over three-consecutive wetting–drying cycles. By further analysing such evolving trend of the axial stress from the perspective of structural degradation, the de-structuration of expansive stiff clay under limited-axial swelling condition could evolve in forms of the desiccation- and hydration-induced cracks growth, diagenetic bonds breakdown and crack sealing during cyclic wetting–drying. Such degradation mechanism needs further verification and quantification by microstructural observations. [ABSTRACT FROM AUTHOR]