Triaxial Axis Shear Mechanical Properties of Fiber-Reinforced Foamed Lightweight Soil

Abstract

Fiber-reinforced foamed lightweight soil is a new type of material that is mixed with cement, foam, polypropylene fiber, and water, and has been applied in the reinforcement of soft soil subgrade. However, it has not yet formed a complete theoretical system. Currently, it is imperative to explore the fiber-reinforced foamed lightweight soil. In this paper, the shear strength characteristics of polypropylene fiber-reinforced foamed lightweight soil with different reinforcement ratios and confining pressures are compared using the global digital systems (GDS) triaxial shear test. It is found that the triaxial shear strength and cohesion first increases, then decreases with the increase of reinforcement ratio, the maximum of which occurs at 0.75% reinforcement rate. The internal friction angle of fiber-reinforced foamed lightweight soil is less affected by the reinforcement ratio. This indicates that the cohesive force of the material is the main factor that affects the strength of the polypropylene fiber-reinforced foamed lightweight soil. The strength reduction rate presents an obvious downward trend with the increase of the reinforcement rate. It reaches from about 40% to 10%, and keeps stable at 10%. From investigating the influence of reinforcement ratio and confining pressure on strength parameters, the research obtains the law of crack propagation of fiber-reinforced foamed lightweight soil and establishes the stress–strain relationship equation. The constitutive equations for the strength parameters of foamed lightweight soil in terms of reinforcement ratio and confining pressure are proposed. After normalizing the experimental data of different reinforcement ratios, the study obtains the stress–strain equation of fiber-reinforced foamed lightweight soil and variation of equation parameters with the influence of stiffening rate and confining pressure.