In Northern climates, waste placed curbside the evening before waste collection can lead to partially frozen waste at placement, which delays biodegradation and biodegradation-induced settlement. A 12-year settlement dataset collected during the filling and post-closure phases at a landfill in Québec, Canada was analyzed. The dataset showed a delay in biodegradation-induced settlement due to the first three waste lifts being placed in the winter months and exhibited an increase in the settlement rate at later times when the waste temperatures increased to values that support biodegradation. The field data also demonstrated that the stiffness of MSW increased in response to confined stress as subsequent waste lifts were added. A thermal-mechanical-biological (TMB) model was developed, in COMSOL Multiphysics, to simulate the settlement dataset. TMB integrates a Generalized Kelvin-Voigt (GKV) model, simulating instantaneous and mechanical creep settlements, with a biodegradation-induced settlement model that relates heat/gas generation with time to biodegradation-induced settlement. The thermal model simulates heat transfer through conduction and includes a biodegradation heat generation source term. The GKV stiffness parameters are expressed as a function of the applied stress to account for waste compressibility effects on mechanical response, which is consistent with field data and the research literature. The paper focuses solely on the MSW settlement field data and model predictions, with thermal response analysis presented in a separate publication. The TMB model effectively predicted waste behaviour, including resistance to compressibility under higher stress and the delay in waste settlement for waste placed in winter. The temperature and settlement data provide a valuable dataset to validate different models that can be used to predict waste settlement in cold regions.
Keywords: COMSOL; Field Data; Frozen Waste; Landfills; Settlement; TMB Model.
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