Influence of dry-wet cycles on the strength behavior of basalt-fiber reinforced loess

Dry-wet cycle induced loess spalling and collapse frequently occurs in the Loess Plateau, which is an influential trigger for the instability of infrastructure. In order to evaluate the resistance of basalt-fiber reinforced loess to dry-wet action, a digital-image system was used in triaxial shear tests with failure mode and shear strength discussed. The apparent feature and microstructure of fiber-reinforced loess were analyzed using the Particles (Pores) and Cracks Analysis System (PCAS) and Scanning Electron Microscope (SEM). Results show that the shear strength of fiber-reinforced loess gradually decreases with dry-wet cycles, with maximum decline after initial two cycles, while it increases and then decreases at higher fiber contents, with pronounced resistance observed at a fiber content of 0.6%. The loess before reinforcement exhibits brittle failure mode while the plasticity becomes more obvious as the fiber content increases, i.e., overall bulging damage but returns to brittle failure after 5 cycles. The crack ratio, as revealed by PCAS, varies consistently with the strength decay after dry-wet cycles. SEM images indicate that microcracks appear in the loess after dry-wet action and the fiber network enhances the resistance to dry-wet cycles, with the deterioration occurring mainly at the soil-fiber interface. Based on the continuum damage theory, a statistical damage model was proposed for fiber-reinforced loess considering dry-wet and loading damage. Error analysis results show that the model well describes the stress-strain behavior of reinforced loess with different fiber contents after dry-wet cycles.