Department of Civil and Materials Engineering, University of Illinois at Chicago, 842 West Taylor Street, Chicago, IL 60607, USA.
Waste Manag. 2011 Nov;31(11):2275-86. doi: 10.1016/j.wasman.2011.06.002. Epub 2011 Jul 20.
This paper presents the results of laboratory investigation conducted to determine the variation of geotechnical properties of synthetic municipal solid waste (MSW) at different phases of degradation. Synthetic MSW samples were prepared based on the composition of MSW generated in the United States and were degraded in bioreactors with leachate recirculation. Degradation of the synthetic MSW was quantified based on the gas composition and organic content, and the samples exhumed from the bioreactor cells at different phases of degradation were tested for the geotechnical properties. Hydraulic conductivity, compressibility and shear strength of initial and degraded synthetic MSW were all determined at constant initial moisture content of 50% on wet weight basis. Hydraulic conductivity of synthetic MSW was reduced by two orders of magnitude due to degradation. Compression ratio was reduced from 0.34 for initial fresh waste to 0.15 for the mostly degraded waste. Direct shear tests showed that the fresh and degraded synthetic MSW exhibited continuous strength gain with increase in horizontal deformation, with the cohesion increased from 1 kPa for fresh MSW to 16-40 kPa for degraded MSW and the friction angle decreased from 35° for fresh MSW to 28° for degraded MSW. During the triaxial tests under CU condition, the total strength parameters, cohesion and friction angle, were found to vary from 21 to 57 kPa and 1° to 9°, respectively, while the effective strength parameters, cohesion and friction angle varied from 18 to 56 kPa and from 1° to 11°, respectively. Similar to direct shear test results, as the waste degrades an increase in cohesion and slight decrease in friction angle was observed. Decreased friction angle and increased cohesion with increased degradation is believed to be due to the highly cohesive nature of the synthetic MSW. Variation of synthetic MSW properties from this study also suggests that significant changes in geotechnical properties of MSW can occur due to enhanced degradation induced by leachate recirculation.
本文介绍了实验室研究的结果，该研究旨在确定不同降解阶段合成城市固体废物（MSW）的岩土特性变化。根据美国产生的 MSW 组成，制备了合成 MSW 样品，并在具有渗滤液再循环的生物反应器中降解。基于气体组成和有机含量来量化合成 MSW 的降解，并对从生物反应器单元中挖掘出的不同降解阶段的样品进行岩土特性测试。在初始含水量为 50%（湿重基础）的恒定初始含水量下，测定了初始和降解合成 MSW 的水力传导率、可压缩性和剪切强度。由于降解，合成 MSW 的水力传导率降低了两个数量级。压缩比从初始新鲜废物的 0.34 降低到大部分降解废物的 0.15。直剪试验表明，新鲜和降解的合成 MSW 随着水平变形的增加表现出连续的强度增长，新鲜 MSW 的凝聚力从 1 kPa 增加到降解 MSW 的 16-40 kPa，新鲜 MSW 的摩擦角从 35°降低到降解 MSW 的 28°。在 CU 条件下进行三轴试验时，发现总强度参数、凝聚力和摩擦角分别在 21 到 57 kPa 和 1°到 9°之间变化，而有效强度参数、凝聚力和摩擦角分别在 18 到 56 kPa 和 1°到 11°之间变化。与直剪试验结果相似，随着废物的降解，凝聚力增加，摩擦角略有降低。随着降解程度的增加，摩擦角减小而凝聚力增加，这被认为是由于合成 MSW 的高粘性。本研究中合成 MSW 特性的变化表明，由于渗滤液再循环引起的降解增强，MSW 的岩土特性可能会发生显著变化。
