Shear behavior of intact loess and spatiotemporal evolution of mesoscopic damage: Dynamic identification using CT technology

The shear behavior of intact loess is intricately linked to the spatiotemporal evolution of its mesoscopic characteristics. Understanding this relationship is crucial for comprehending and preventing loess landslides. To systematically investigate this connection, our study conducted triaxial shear tests on both Malan loess and Lishi loess, encompassing variations in confining pressures. Additionally, non-destructive, real-time CT observations were employed to track the dynamic evolution of loess mesostructures. The experimental findings illuminate significant insights. The Malan loess exhibits strain hardening during shearing, with the degree of hardening exhibiting an increase in tandem with rising confining pressure. Conversely, the Lishi loess manifests a transition from strain softening to strain hardening as confining pressure increases. Under elevated confining pressure, the specimen undergoes structural damage while concurrently forming a denser configuration through particle friction and rearrangement, leading to strain hardening and volume reduction. In contrast, the central portion of the specimen exhibits heightened sensitivity to deformation under low confining pressures. Gradual crack expansion, emanating from the center and progressing towards the ends, results in progressive specimen destruction and a concomitant reduction in stress. On a macroscopic level, the specimen undergoes expansion at its center while contracting at its ends. The findings of this study unveil the intricate mechanisms governing loess deformation in the presence of varying confining pressures, thereby contributing significantly to our understanding of loess landslide formation and providing a robust theoretical framework for preventive measures.