A Fiber-Reinforced Constitutive Model for Earthen Materials in Partially Saturated Conditions

A new elasto-plastic constitutive model for fiber-reinforced materials is developed. The model considers the effect of distributed fibers embedded in a matrix. The effect of the tensile stresses in the fibers is integrated numerically over possible orientations to convert it into a homogenized composite material stress. The fiber model considers both the degradation of the cohesive bond due to fiber-matrix interface mechanism, the elasto-plastic behavior of the fibers and their ultimate strength. Fiber model is coupled with the constitutive model of the soil matrix to obtain the constitutive model of fiber reinforced soil. Additionally, the soil model is embedded in a partially saturated framework. A mixed finite element formulation is employed to account for the coupling of the solid skeleton and pore liquid. The dry case and the fully saturated case are obtained as special cases of the partially saturated formulation. A finite element code is developed in Matlab to implement the coupled formulation. The finite element code for the soil with no fibers is verified with several numerical examples with known solutions from literature. Furthermore, the fiber-reinforced material is used to investigate the behavior of various structural elements in partially saturated conditions and loading, with the overall goal of improving the mechanical behavior of this material.