Study on Strength Behavior of Basalt Fiber-Reinforced Loess by Digital Image Technology (DIT) and Scanning Electron Microscope (SEM)

Basalt fiber has unique advantages in the reinforcement of slopes and foundation. In this study, triaxial shear tests under undrained unconsolidated conditions, digital image technology and scanning electron microscope (SEM) tests were carried out to investigate the mechanism of fiber reinforcement to improve the shear strength of loess. Results show that the shear strength of reinforced sample is significantly higher than that of the unreinforced case, but not monotonically with increasing fiber length or fiber content, but with a maximum value at 0.6% fiber content and 12 mm fiber length. The failure morphology and strain field indicate that samples at higher fiber content exhibit bulging failure while those without fiber or at low fiber content show shear band failure. SEM images implies that the fibers in the soil tend to be orderly distributed as the fiber content increases while prone to bending and entanglement as the fiber length grows, which limits the mechanical response of the fibers. The statistical analysis proves that the hyperbolic strength model fits better than the parabola in the tension-shear and the shear domain. A unified joint strength model for basalt fiber-reinforced loess was obtained by fitting test data under different fiber contents and its rationality was verified by the error analysis.