Experimental study on ring shear properties of fiber-reinforced loess

Abstract

With poor mechanical properties and engineering characteristics, loess soils alone cannot meet the requirements of high-speed railway subgrade and large-sized building foundations based on shear strength and bearing capacity. Therefore, it is necessary to improve the mechanical properties of loess. In soil reinforcement, encouraging outcomes have been achieved by using fibers as reinforcement material for its relatively low costs and the low environment impact results from this material. To investigate the mechanical properties and the reinforcement mechanism of fiber-reinforced loess, ring shear tests were performed on loess samples with varying polypropylene fiber contents (0%, 0.25%, 0.50%, 0.75%, and 1%) and moisture contents (12%, 14%, 16%, 18%, and 20%). Furthermore, the macroscopic structure and microscopic images of the shear plane of reinforced specimens were analyzed as well. The test results showed that firstly polypropylene fibers significantly improved the peak strength and the residual strength of loess, and the optimal fiber content and the optimal moisture content were found to be 0.5% and 16%, respectively. The theoretical relationships between the fiber content Fc, the moisture content Mc, the peak strength τ, and the residual strength τr of reinforced loess were quantitatively determined. In addition, the fiber reinforcement mechanism was revealed based on the macroscopic shear plane of fiber-reinforced loess and SEM microscopic images of the shear plane.