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CLC number: TU43; X5

On-line Access: 2016-08-05

Received: 2015-03-28

Revision Accepted: 2016-01-19

Crosschecked: 2016-07-28

Cited: 0

Clicked: 1732

Citations:  Bibtex RefMan EndNote GB/T7714

 ORCID:

Chi Guan

http://orcid.org/0000-0001-6617-6576

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Journal of Zhejiang University SCIENCE A 2016 Vol.17 No.8 P.667-676

10.1631/jzus.A1500073


One-dimensional coupled model for landfill gas and water transport in layered unsaturated soil cover systems


Author(s):  Chi Guan, Hai-jian Xie, Zhan-hong Qiu, Yun-min Chen, Pei-xiong Chen

Affiliation(s):  School of Business Administration, Zhejiang Gongshang University, Hangzhou 310038, China; more

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

Key Words:  Landfill gas, Cover systems, Unsaturated soils, Gas-water transport, Coupled model


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Chi Guan, Hai-jian Xie, Zhan-hong Qiu, Yun-min Chen, Pei-xiong Chen. One-dimensional coupled model for landfill gas and water transport in layered unsaturated soil cover systems[J]. Journal of Zhejiang University Science A, 2016, 17(8): 667-676.

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%T One-dimensional coupled model for landfill gas and water transport in layered unsaturated soil cover systems
%A Chi Guan
%A Hai-jian Xie
%A Zhan-hong Qiu
%A Yun-min Chen
%A Pei-xiong Chen
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T1 - One-dimensional coupled model for landfill gas and water transport in layered unsaturated soil cover systems
A1 - Chi Guan
A1 - Hai-jian Xie
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A1 - Yun-min Chen
A1 - Pei-xiong Chen
J0 - Journal of Zhejiang University Science A
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DOI - 10.1631/jzus.A1500073


Abstract: 
cover systems are used to prevent water infiltration into a waste body. They also play an important role in controlling landfill gas transport from the waste body to the atmosphere. It is important to assess the flux of landfill gas at the surface of a cover system by considering the coupled effects of rainwater infiltration and gas transport in the cover soils. We have developed a 1D mathematical model for coupled transient gas and water transport in unsaturated cover soils. The coupled model was solved by the finite element method. Results obtained by the proposed model agreed well with experimental data. Based on the proposed solution, the influences of gas pressure, gas permeability, and the thickness of the cover soils on soil gas concentration profiles were investigated. The difference in soil gas concentration reached up to 31% as the thickness of cover increased from 1 to 2 m. Gas concentration at a depth of 0.2 m decreased by 6% as the amplitude of atmospheric gas pressure fluctuation increased from 20 to 100 Pa. The gas concentration increased by only 3% when gas permeability increased by a factor of 2 for a relatively long period of gas migration (e.g., 60 h) under the given conditions. Results suggest that both diffusion and advection should be considered when estimating gas transport in unsaturated cover soils. The numerical model can be used in the design of cover systems in relation to gas breakthrough time, breakthrough concentration, and flux.

The authors attemped to develop an one-dimensional coupled model for gas and moisture transport in layered soil cover systems at landfills. The model was solved by using the commercial software (COMSOL). Parametric study was carried out to investigate the influences from atmospheric gas pressure, gas permeability and thickness of soil cover on the distribution of gas concentration. The study is of interest to the researchers in the area of geoenvironmental engineering. Overall, the technical approach is solid, and results and conclusions appear to be reasonable.

填埋场非饱和成层覆盖层一维气水耦合运移模型

目的:为更好地评价填埋场覆盖层系统的闭气性能,建立水气耦合条件下的覆盖层中气体运移模型。在此基础上分析大气压强波动、渗透系数变化和对流扩散等因素耦合作用下填埋气在覆盖层中的运移规律。
创新点: 建立水气耦合条件下填埋气在覆盖层中的运移模型,分析多种因素耦合作用下填埋气的运移过程,并比较对流运移和扩散运移的相对重要性。
方法:1. 通过理论分析,建立考虑压强、对流、扩散和非饱和情况的填埋气耦合运移模型;2. 通过试验拟合,得到大气压强波动的拟合经验公式(公式(22)),构建考虑压强波动下填埋气多场耦合运移模型;3. 通过仿真模拟,验证所建模型的可行性和正确性(图2),并分析包含大气压强波动和渗透率等影响因素作用下填埋气的运移规律(图6~8)。
结论:1. 覆盖层厚度从1米变化到2米,覆盖层中填埋气的浓度变化可达31%;2. 对于受大气压强波动影响较大的覆盖层系统(如1×103 Pa),不能忽略压强波动对填埋气运移的影响; 3. 气体渗透系数在初期对气体运移有较大影响,随运移时间增加直至气体运移达到稳定状态,渗透率的影响可以忽略(仅3%)。

关键词:填埋气;覆盖层系统;非饱和土;气水运移;耦合模型

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

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