A hydro-bio-mechanical model for settlement and other behaviour in landfilled waste

A conceptual framework for the analysis of settlement and other processes in landfilled waste in relation to coupled hydraulic, biodegradation and mechanical behaviour is presented. The hydraulic model is an unsaturated flow model. The biodegradation model is a two-stage anaerobic digestion model modified to account for enzymatic hydrolysis of solid degradable matter in relation to moisture content, product inhibition, cellulose digestibility and microbial controls. The mechanical model includes an innovative interpretation of the mechanical consequences of decomposition combined with established formulations of load and creep-induced effects to predict settlement under load and over time. A finite element implementation enables simulation of both the filling phase and leachate control practices. Finally, the formulation is tested by comparison with a large-scale laboratory waste compression test.