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Multi-Physical Analysis of Thermal, Hydraulic, Mechanical, and Bio-Chemical (THMB/C) Processes in a Municipal Solid Waste Landfill

M. Sina Mousavi, University of Nebraska - Lincoln

Abstract

Municipal solid waste (MSW) landfills recirculate leachate to increase efficiency in leachate and biogas management while this practice creates complex thermal, hydraulic, mechanical, and bio-chemical (THMB/C) processes inside the waste. Considering spatial and temporal changes to MSW in a landfill, a thorough understanding of these processes is necessary to determine MSW settlement behavior to prevent landfill failure. In this study, the multiphysical (i.e., THMB/C) processes were investigated to understand short-term and long-term MSW behavior (e.g., MSW slope stability and settlement) by using small-scale and large-scale experiments at different biodegradation and temperatures. In the small-scale bioreactor test, the results showed that a temperature of 78 °C increased compressibility by 17.6%, and more biodegradation decreased the compressibility by an average of 46%. To characterize MSW unsaturated properties, three modified hanging column tests were conducted with low and medium compacted MSW samples. The stability analysis of MSW landfill slope using GeoStudio with the input properties from the unsaturated experiment showed that hydraulic properties, subgrade conditions, and leachate and gas collection systems have a significant impact on landfill slope stability. Three large-scale column tests at different temperatures and saturation were used to evaluate MSW bio-chemical and mechanical behavior, including biogas production, leachate quality, and settlement. Biodegradation onset decreased from 40 to 7 days when optimum conditions were applied. Based on the results, a predictive modeling framework was developed to estimate MSW settlement subjected to THMB/C processes, and was validated by comparing to a field-testing result. The developed model results give most accurate settlement prediction when compared to known models that fail to consider temperature and saturation. Finally, field tests using membrane interface probe with hydraulic pressure tool and cone penetration testing (CPT) equipment in active and closed landfills obtained vertical profiles of the landfill to measure methane, hydraulic pressure, electrical conductivity, and CPT values. It was found that there is potential to use direct-push tools for MSW characterization due to parameter changes with biodegradation and depth.

Subject Area

Civil engineering|Design

Recommended Citation

Mousavi, M. Sina, "Multi-Physical Analysis of Thermal, Hydraulic, Mechanical, and Bio-Chemical (THMB/C) Processes in a Municipal Solid Waste Landfill" (2021). ETD collection for University of Nebraska - Lincoln. AAI28652987.
https://digitalcommons.unl.edu/dissertations/AAI28652987

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