Experimental Investigation of the Effect of Fibrous Reinforcement on Shear Resistance of Soil-Waste Mixtures

Abstract

The effect of fibrous waste reinforcement on the shear resistance of soil-waste mixtures is experimentally investigated using a large (30 cm × 30 cm × 18 cm) direct shear box. Analogies in shear response to fiber-reinforced soils (FRS) are identified. Specimens are reconstituted at varying fibrous waste orientations using a custom-made specimen preparation split mold. Tests on soil-waste mixtures with waste fibrous constituents, i.e., paperboard, plastic and wood, commonly encountered in municipal solid waste (MSW) landfills are performed. Fibrous constituents are characterized by performing tensile tests and interface testing. The experimental data confirms that the shearing response of soil-waste mixtures is analogous to that of FRS and provides a basis for explaining the fiber reinforcement effect of MSW. It was found that the presence of fibrous constituents results in significant anisotropy in shear resistance of the direct shear specimens with fiber reinforcement contribution being a function of the reinforcement orientation and the type of fiber. The impact of reinforcement orientation on the shear strength of the specimens is significant. The largest increase in shear resistance of the specimens is observed for a reinforcement angle of 60° with respect to the shear plane, consistent with findings of previous studies on FRS. Wood fibers exhibit the highest tensile strength and the lowest strain at failure as well as the highest interface strength with soil, compared to paperboard and plastic fibers. Wood fibers also contribute the most to the shear resistance of soil-waste mixtures. For these mixtures, similarly to FRS, once the amount of reinforcement exceeds a certain threshold, it does not contribute further to reinforcement. Results of this investigation indicate that the previously recommended strength envelopes for MSW may not account for the significant fibrous reinforcement effect, although lower shear resistances may be observed in direct shear when shearing occurs parallel to plastic fibrous constituents.