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CLC number: TU43

On-line Access: 2016-07-05

Received: 2016-03-15

Revision Accepted: 2016-06-08

Crosschecked: 2016-06-16

Cited: 0

Clicked: 1071

Citations:  Bibtex RefMan EndNote GB/T7714

 ORCID:

Liang-tong Zhan

http://orcid.org/0000-0002-4483-6737

Qing-wen Qiu

http://orcid.org/0000-0001-9296-391X

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Journal of Zhejiang University SCIENCE A 2016 Vol.17 No.7 P.541-552

10.1631/jzus.A1600245


Field measurement of gas permeability of compacted loess used as an earthen final cover for a municipal solid waste landfill


Author(s):  Liang-tong Zhan, Qing-wen Qiu, Wen-jie Xu, Yun-min Chen

Affiliation(s):  MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou 310058, China

Corresponding email(s):   zhanlt@zju.edu.cn

Key Words:  Compacted loess, Capillary barrier cover, Gas permeability, Volumetric water content, Landfill


Liang-tong Zhan, Qing-wen Qiu, Wen-jie Xu, Yun-min Chen. Field measurement of gas permeability of compacted loess used as an earthen final cover for a municipal solid waste landfill[J]. Journal of Zhejiang University Science A, 2016, 17(7): 541-552.

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Abstract: 
The use of loess as an earthen final cover material is promising in northwest China which has an arid and semi-arid climate. A full-scale testing facility with an area 30 m long by 20 m wide was constructed at the Xi’an landfill of municipal solid wastes to investigate the performance of an inclined capillary barrier cover. The cover consisted of a compacted loess layer underlain by a gravel layer. The testing facility was well instrumented for a gas permeation test and recording of the soil conditions in terms of volumetric water content, pore gas pressure, and soil temperature. Tests were performed to measure the gas permeability of the compacted loess before and after the planting of vegetation on the cover. The field measurements demonstrate that the capillary break at the fine/coarse soil interface allows the upper compacted loess layer to retain more water, and conversely reduces its gas permeability, which is favorable for reducing landfill gas emissions. When the degree of saturation of the compacted loess was greater than 85%, the gas permeability decreased significantly with a further increment in volumetric water content. The growth of vegetation roots tended to fill the large pores in the upper loosely-compacted loess, resulting in a decrease in gas permeability of one order of magnitude. The influence of soil clods in the compacted loess on gas permeability can be one to two orders of magnitude due to an increase in pore size and a decrease in tortuosity.

This manuscript describes field measurement of gas permeability of a compacted loess that is proposed to be used as a final cover material for MSW landfill in Northwest China. The results provided by the authors are of interest to the researchers and practitioners from the field of landfill covers since the field experimental results of gas permeability of unsaturated loess have been rarely published in the literature. The experimental setup, instrumentation and procedure are provided in details. The authors do have some good descriptions and explanations of test results. However, a more in-depth interpretation of experimental data may help the readers to better understand the scale effect for field measurement as compared with laboratory measurement.

现场测试固废填埋场压实黄土覆盖层的气相渗透系数

目的:我国西北地区黄土分布广泛,黄土作为当地固废填埋场的覆盖土料具有广泛的应用前景。现场尺度测试压实黄土覆盖层的气相渗透系数,从而可用于评估其填埋气减排性能。
方法:1. 在西安固废填埋场建立压实黄土覆盖层试验基地(图2);2. 在试验基地的膜内核心测试区域布置通气试验系统,包括空气压缩机、通气管网、气压测试装置、含水率测试装置、温度传感器和静态箱(图3, 5~7);3. 在覆盖层表面裸露时和植草后分别进行通气试验测试压实黄土覆盖层的气相渗透系数。
结论:1. 当饱和度低于85%时,干密度为1.45 Mg/m3压实黄土的气相渗透系数随含水率增加而降低,但并不明显;但是当饱和度高于85%时,气相渗透系数随含水率增加而显著减小;2. 黄土层和碎石层之间的毛细阻滞作用使得上部黄土层储存更多水分,并显著降低其气相渗透系数,这有利 于降低填埋气的排放;3. 裸露条件下,当压实黄土的体积含水率从36%增加至46%时,其气相渗透系数从3.67×10-12 m2 降低至5.73×10-14 m2; 4. 植草后压实黄土的气相渗透系数比裸露条件下小近一个数量级,这主要是因为植被根系占据了压实黄土的大孔隙;5. 现场尺度的压实黄土气相渗透系数比室内试验的结果高1至2个数量级,这主要是因为现场所用黄土含有大的结团,结团会增加黄土的孔隙直径以及减小孔隙的曲折度。

关键词:压实黄土;毛细阻滞型覆盖层;气相渗透系数;体积含水率;填埋场

Darkslateblue:Affiliate; Royal Blue:Author; Turquoise:Article

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