Modeling elasto-visco-bio-plastic mechanical behavior of municipal solid waste in landfills

Abstract

This paper presents a mechanical model for the prediction of short-term and long-term settlement of municipal solid waste in landfills. The load-induced volumetric compression, shear behavior, tensile behavior, and the time-dependent creep compression behavior of the waste are modeled using the soft soil creep model. The compression induced by decomposition of waste is modeled based on the phenomenon of wetting-induced strains observed in compacted fills with expansive soils. The proposed model is validated using benchmark datasets obtained from two long-term laboratory experiments performed on waste samples obtained from a landfill in UK. Two additional numerical simulation cases (CONV—without leachate injection and BIOR—with leachate injection) were examined by application of the proposed mechanical model on a typical full-scale landfill cell geometry to determine the spatial and temporal variation in the short-term and long-term settlement characteristics of waste in the simulated landfill cell. The settlement of waste predicted by the model could capture the key mechanisms of short- and long-term waste settlement in landfills. The leachate injection in BIOR simulation enhanced the rate of depletion of the degradable solids resulting in a significant increase in the waste settlement. For the simulated landfill and waste conditions, the biodegradation-induced settlement contributed to more than 90% of the settlement of the waste in both CONV and BIOR simulations. The distribution of the injected leachate had a considerable influence on the settlement profiles observed within the waste.