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Geomechanics and Engineering Volume 33, Number 2, April25 2023 , pages 141-154 DOI: https://doi.org/10.12989/gae.2023.33.2.141 |
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Effect of variation of water retention characteristics due to leachate circulation in municipal solid waste on landfill stability |
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M. Sina Mousavi, Yuan Feng, Jongwan Eun and Boo Hyun Nam
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| Abstract | ||
| This study investigated the effect of water retention characteristics between aged and fresh Municipal Solid Waste (MSW) on the stability of the landfill. A series of transient numerical modeling for the slope of an MSW landfill was performed considering the variation of water retention characteristics due to leachate circulation. Four different scenarios were considered in this analysis depending on how to obtain hydraulic conductivity and the aging degree of materials. Unsaturated hydraulic properties of the MSW used for the modeling were evaluated through modified hanging column tests. Different water retention properties and various landfill conditions, such as subgrade stiffness, leachate injection frequency, and gas and leachate collection system, were considered to investigate the pore water distribution and slope stability. The stability analyses related to the factor of safety showed that unsaturated properties under those varied conditions significantly impacted the slope stability, where the factor of safety decreased, ranging between 9.4 and 22%. The aged materials resulted in a higher factor of safety than fresh materials; however, after 1000 days, the factor of safety decreased by around 10.6% due to pore pressure buildup. The analysis results indicated that using fresh materials yielded higher factor of safety values. The landfill subgrade was found to have a significant impact on the factor of safety, which resulted in an average of 34% lower factor of safety in soft subgrades. The results also revealed that a failed leachate collection system (e.g., clogging) could result in landfill failure (factor of safety < 1) after around 298 days, while the leachate recirculation frequency has no critical impact on stability. In addition, the accumulation of gas pressure within the waste body resulted in factor of safety reductions as high as 24%. It is essential to consider factors related to the unsaturated hydraulic properties in designing a landfill to prevent landfill instability. | ||
| Key Words | ||
| coupled analysis; municipal solid waste; numerical modeling; slope; unsaturated hydraulic properties | ||
| Address | ||
| M. Sina Mousavi, Yuan Feng and Jongwan Eun: Department of Civil and Environmental Engineering, University of Nebraska-Lincoln, Nebraska, USA Boo Hyun Nam: Department of Civil Engineering, Kyung Hee University, Seoul, South Korea | ||