A constitutive model for municipal solid waste incorporating bounding surface plasticity and reinforcing effect

Seismic stability of municipal solid waste (MSW) landfills is of vital importance and increasingly encouraged to be analyzed through numerical modeling where a rational definition of the stress-strain relationship of MSW is essentially required. The complicated constituents and existence of fibrous materials lead to mechanical behaviors totally different from general soils. In this study, a constitutive model is proposed to describe the dynamic response of MSW. This model is based on the double-phase assumption, i.e. the behaviors of the MSW whole are governed by the basic and fibrous phase. The basic phase is described with a bounding surface plasticity model considering the degradation effect under dynamic loadings, and the fibrous phase is described with a pressure-dependent elastic model. An explicit integration algorithm with automatic error control is applied to solve it. The coupling of these two constitutive models facilitates the continuous development of effective stress path over the critical state line, which reflects the reinforcing effect of fibrous materials. Furthermore, the compression of MSW particles is considered for undrained conditions, enabling the accurate calculation of effective stress. This model is verified through comparison with triaxial test results and its features are demonstrated through parametric studies and application in specific problems.