Comprehensive coupled thermo-hydro-bio-mechanical model for holistic performance assessment of municipal solid waste landfills

A comprehensive coupled thermo-hydro-bio-mechanical (CTHBM) model is proposed to simulate the coupled interactions between the hydraulic, mechanical, biochemical, and thermal processes observed in municipal solid waste (MSW) and also assess their influence on the long-term performance of MSW landfills. The hydraulic model is based on two-phase fluid flow through unsaturated porous media. The biochemical model is based on a two stage anaerobic biodegradation model. The thermal model is based on conductive heat transport with heat generation rates derived from the biodegradation model. The mechanical model uses the soft-soil-creep constitutive model to simulate the time-dependent creep behavior of the waste. The effect of biodegradation and subsequent mass loss on the waste settlement is also incorporated. Using the proposed CTHBM model, two numerical simulations were performed on a typical full-scale landfill cell geometry to determine the long-term spatial and temporal variations in the hydraulic, mechanical, biochemical, and thermal characteristics of waste under conventional and bioreactor landfill conditions. The influence of the dynamic changes in the waste characteristics on the shear behavior of a textured geomembrane-geotextile interface in the bottom liner and cover system of the simulated landfill cell was also examined.