Modeling Coupled Dynamic Processes in Landfills: Holistic Long-Tern Performance Management to Improve Sustainability

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Many engineered landfills that accept municipal solid waste are classified as "dry tomb landfills" because waste degrades very slowly due to low moisture conditions. As an alternative, bioreactor landfills have emerged to counter those conditions. In bioreactor landfills, leachate recirculation systems increase moisture and accelerate degradation. The performance of bioreactor landfills results from coupled hydro-bio-mechanical processes; however, industry lacks a comprehensive, holistic mathematical model that considers and effectively analyzes these coupled processes in landfills. This project will develop a new coupled mathematical tool to enable the design and operation of stable, effective and sustainable engineered landfills, thereby minimizing long-term risks to the surrounding environment and public. The tool will enable practitioners and regulators to predict the highly complex landfill stabilization period, and allow for the planning of beneficial reuse of landfill space, such as recreational facilities, by accurately accounting for a differential settlement and stabilization period. With controlled, predictable, rapid municipal solid waste decomposition and a reduced stabilization period: (a) non-degradable municipal solid waste may be mined and processed, reducing the amount of landfill mass encapsulated within a landfill; (b) post-closure monitoring can be shortened and associated expenditures considerably reduced; and (c) concerns about the long-term performance of geosynthetic liners and related environmental risks can be addressed. This research involves multiple disciplines, including geoenvironmental engineering, sustainable engineering, biology, and computational mechanics. The multi-disciplinary research will provide a unique opportunity to underrepresented groups to participate in research.The proposed modeling tool will combine and simultaneously solve a two-phase flow model, a large-strain explicit mechanical model, and a first-order decay biodegradation model. The model will account for concurrent changes in waste properties to predict coupled processes in landfills. Specifically, the project scope will include: (a) development of a new mathematical model that can account for heterogeneous waste, two-phase flow, and coupled hydro-bio-mechanical processes, and effectively predict spatial and temporal behavior of landfills, (b) model validation with laboratory and field studies to attain a confidence level in the accuracy of the modeling results, (c) prediction of spatial and temporal landfill settlement, slope stability and shear response of liner systems due to coupled processes, (d) assessment of the major system variables that control the performance of landfills based on probabilistic analysis, and (e) application of the tool for forensic investigation of past landfill failures. The project will provide a tool for designing stable and effective engineered landfills and optimizing existing landfills using coupled hydro-bio-mechanical processes.