A double-phase constitutive model for municipal solid waste with a fiber pullout criterion to evaluate the softening behavior

Abstract

Flowslide disasters of municipal solid waste (MSW) landfills generally have a long flow distance. In the condition of extremely large deformation, the strength of MSW cannot be reinforced by embedded fibers (also called hardening) with fiber pullout. To describe this softening behavior of MSW in a state of large strain, this study proposes a double-phase constitutive model with a fiber pullout criterion. The mechanical response of MSW is attributed to the basic phase and the fibrous phase described by the modified Cam-Clay (MCC) model with an extension and a pressure-dependent elastic model, respectively. The fiber pullout criterion is governed by the shear stress acting on the fiber-particle interface and the stress state of the fibrous phase. The compressibility of MSW particles is also considered to well reproduce the variations of effective stress in undrained conditions. The model is verified with the previous triaxial tests in drained and undrained conditions, and the mechanism of MSW softening behavior is revealed through a parametric study. Results show that the fiber pullout occurs before the strength of MSW reaches its peak and the stress state remains stable when all fibers are pulled out.