Study on Mechanical Properties and Microstructure of Basalt Fiber-Modified Red Clay

The effects of basalt fiber incorporation on the mechanical properties of red clay soils were investigated. Through the direct shear test, unconfined compressive strength test, and microstructure test, the shear strength curves and stress–strain curves of basalt fiber-modified red clay soils were obtained under different basalt fiber incorporation rates and different soil dry density conditions. The results showed that: (1) the shear strength and compressive strength of the soil were significantly increased after the incorporation of basalt fiber; (2) the strength increase was greatest at 0.3% of basalt fiber incorporation, which was the optimum incorporation level; (3) the damage form of the soil changed, and the red clay soil incorporated with basalt fiber changed from brittle damage to ductile damage; and (4) the microscopic electron microscope pictures showed that, at the appropriate amount of fiber incorporation conditions, the fiber bond with the soil particles and form a fiber‒soil column. When subjected to external forces, the discrete fiber‒soil columns interact with each other to form an approximate three-dimensional fiber‒soil network, which acts to restrain the displacement and deformation of the soil particles, which is the main reason for the improved mechanical properties of the improved soil. The experimental research on the improvement of red clay soil with basalt fiber can provide a theoretical basis for engineering practice and help provide an environmentally friendly and efficient method of road base treatment in engineering.