Abstract: In this paper, the digital image based triaxial shear, CT scanning and SEM tests were employed to investigate triaxial shear behavior and microstructure evolution of basalt fiber reinforced loess under drying-wetting action. The results show that the shear failure morphology of soil samples with relatively higher basalt fiber content changes from overall bulging to shear band failure with increasing drying-wetting cycles, while it exhibits the opposite variation with increasing fiber content at the early stage of drying-wetting process. Drying-wetting cycles and fiber content have no obvious effect on the type of stress-strain curves, which present strain hardening behavior. The deviator stress at failure decreases with the increasing number of drying-wetting cycles; however, the attenuation rate gradually decreases. The deviator stress at failure shows a parabolic variation with increasing fiber content and the optimal fiber content is 0.6%. A similar trend is observed between the ME value of CT scanning and the deviator stress at failure. Drying-wetting action induces cracking and loosening around the soil-fiber interface, thus weakening the fiber reinforcement effect. However, compared with unreinforced loess, fiber reinforced loess demonstrates strong stability in its microstructure. The macroscopic and microscopic damage variables reflecting the drying-wetting induced deterioration of loess samples were finally established, which shows consistent trend.

Key words: drying-wetting cycles, basalt fiber reinforced loess, digital image technology, triaxial shear test, damage variable