Composite Compressibility Model for Municipal Solid Waste

Three important mechanisms that contribute to the compression of municipal solid waste are instantaneous compression in response to applied load, secondary mechanical creep, and time-dependent biological decomposition. A composite compressibility model that explicitly takes these mechanisms into account was developed and implemented in a computer program to calculate landfill settlements. The model performance was assessed using data from the Bandeirantes Landfill, which is a well-documented landfill located in Sao Paulo, Brazil, and upon which an instrumented test fill was constructed. Model parameter values were obtained by nonlinear regression analysis, and it was found that the composite model tracked observed patterns of landfill settlement very well. Furthermore, the average parameter values from nonlinear regression analyses for 20 instruments exhibited small deviations between calculated and observed settlements, indicating that a single set of parameter values can provide reasonably good representation of all the waste in the vicinity of the test fill. Recommendations for applying the model to other landfills are provided.