Dynamic Properties of Municipal Solid Waste in Bioreactor Landfills with Degradation |
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| Authors: | M S Hossain M A Haque L R Hoyos |
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| Institution: | (1) Department of Civil and Environmental Engineering, University of Texas at Arlington, Arlington, TX 76019, USA;(2) Bryant Consultants, Inc., Carrollton, TX 75006, USA |
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| Abstract: | Bioreactor landfills are operated to enhance refuse decomposition, gas production, and waste stabilization. The major aspect
of bioreactor landfill operation is the recirculation of collected leachate back through the refuse mass. Due to the presence
of additional leachate and accelerated decomposition, the characteristics of Municipal Solid Waste (MSW) in bioreactor landfills
are expected to change. About 50% of the continental United States comes under the designated seismic impact zone. The federal
regulations have focused increase attention on seismic design of solid waste fills, and have mandated that the solid waste
landfills located in the seismic impact zones should be designed to resist the earthquake. Accordingly, assessment of dynamic
properties of landfills is one of the major geotechnical tasks in landfill engineering. In order to understand the changes
in dynamic properties of bioreactor waste mass with time and decomposition, four small scale bioreactor landfills were simulated
in laboratory and samples were prepared to represent each phase of decomposition. The state of decomposition was quantified
by methane yield, pH, and volatile organic content (VOC). A number of Resonant Column (RC) tests were performed to evaluate
the dynamic properties (stiffness and damping) of MSW. The test results indicated that the normalized shear modulus reduction
and damping curves are significantly affected by the degree of decomposition. The shear modulus increased from 2.11 MPa in
Phase I to 12.56 MPa in Phase IV. The increase was attributed to the breakdown of fibrous nature of solid waste particles
as it degrades. Therefore, considering MSW properties to be uniform throughout the bioreactor landfill is not a reasonable
assumption and the shear modulus reduction curves should be evaluated based on the degree of MSW decomposition, rather than
the sample composition itself. |
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