Interpretation of mechanical and biodegradation behaviour of municipal solid waste

An advanced constitutive model for MSW (municipal solid waste) is proposed in this study to consider biodegradation and overconsolidation jointly based on sub-loading surface plasticity. A reference line, namely the BNCL (biodegradation-independent normally compression line), is introduced to quantify the total biodegradation time and overconsolidation state of MSW. Under unchanged stress level, the void ratio change due to biodegradation is interpreted as the change of overconsolidation. An isotropic stress–strain-biodegradation constitutive model is then proposed by considering biodegradation-dependent deformation through overconsolidation parameter. The current yield surface and the reference yield surface are introduced for assessing the effect of overconsolidation (biodegradation has been included). The isotropic model is then extended to a triaxial stress state in the space of mean effective stress, deviator stress and biodegradation variable. The performance of the constitutive model is discussed through various scenarios and validated by using experimental data from the literature.