A fiber-reinforced constitutive model for earthen materials in partially saturated conditions

Abstract Earthen materials often suffer from being relatively weak in tension. The degree of saturation can also greatly influence this strength. One possible improvement method is the use of distributed fiber reinforcement within the soil to improve strength and, in extreme loading, ductility. In this research, we develop a partially saturated soil model to couple with a recently developed model for fiber-reinforced materials. The coupling of the solid skeleton and pore liquid pressure is modeled using a mixed formulation. The gas phase is assumed to remain at atmospheric pressure. The fiber-reinforcement model homogenizes the fibers using an orientation distribution function, and accounts for fiber plasticity, slipping with respect to the matrix, and breakage. The model is implemented in a custom finite element code. The partially saturated formulation without fibers is verified using known solutions from the literature. The model is then used to investigate the behavior of partially saturated earthen structural elements, to understand the effect of fiber reinforcement and partial saturation on structural behavior.