A comparative study of selected models simulating the settlement of municipal solid waste (MSW) with a focus on landfills in northern climates

Abstract

Evaluating model parameters through laboratory experiments presents challenges due to waste heterogeneity and scale effects. This study investigates the settlement response of selected models using field-scale data collected from the filling and post-closure phases of the Ste. Sophie landfill in Canada. The first model was based on primary and secondary compression ratios, which could capture the overall settlement but ignored the effect of freezing temperatures on biodegradation-induced settlement. The second model was a composite model with a primary compression ratio, and rheological and first-order decay equations. The model failed to accurately simulate mechanical creep and account for the effect of freezing temperatures. A modified version, with mechanical creep expressed as a function of the applied stress, was proposed and showed improved settlement predictions. The third model was a Generalized Kelvin-Voigt (GKV) model with biodegradation-induced strain expressed as a function of waste expended energy. This model could simulate the field settlement by considering resistance to compressibility and effects of freezing temperatures. The final model was based on the Modified Cam-Clay (MCC) model. Several studies in the literature have extended the MCC yield surface by incorporating specific mechanical and biological creep models. In this study, a general procedure was proposed to integrate time-dependent strain into the MCC yield surface, irrespective of the mechanical and biological creep models used. The extended MCC model revealed an unrealistic increase in preconsolidation pressure, resulting in an initial elastoplastic response followed by a pure elastic response. It also provided a poor estimation of the field settlement.