Evaluating gas breakthrough pressure and gas permeability in a landfill cover layer for mitigation of hazardous gas emissions

Shaojie Wen; Wen-Chieh Cheng; Dongfeng Li; Wenle Hu

doi:10.1016/j.jenvman.2023.117617

Evaluating gas breakthrough pressure and gas permeability in a landfill cover layer for mitigation of hazardous gas emissions

J Environ Manage. 2023 Jun 15:336:117617. doi: 10.1016/j.jenvman.2023.117617. Epub 2023 Mar 7.

Authors

Shaojie Wen¹, Wen-Chieh Cheng², Dongfeng Li³, Wenle Hu⁴

Affiliations

¹ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: wenshaojie@xauat.edu.cn.
² School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: w-c.cheng@xauat.edu.cn.
³ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: ldf@xauat.edu.cn.
⁴ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China; Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering (XAUAT), Xi'an, 710055, China. Electronic address: wenlehu@xauat.edu.cn.

PMID: 36967689
DOI: 10.1016/j.jenvman.2023.117617

Abstract

The construction of an engineered cover layer over landfills is a common method applied to reduce the emission of hazardous gases into the atmosphere. Landfill gas pressures can reach 50 kPa or even higher in some cases, thus posing a serious threat to nearby properties and human safety. As such, the evaluation of gas breakthrough pressure and gas permeability in a landfill cover layer is of great necessity. In this study, the loess soil that is often applied as a cover layer in landfills in northwestern China was used to conduct gas breakthrough, gas permeability, and mercury intrusion porosimetry (MIP) tests. Resultantly, the smaller the capillary tube diameter, the higher the capillary force, and the more significant the capillary effect. Gas breakthrough could be attained with no difficulty, provided that the capillary effect was minimal or approached zero. A good fit between the experimental gas breakthrough pressure-intrinsic permeability relationship and a logarithmic equation was found. The mechanical effect blew up the gas flow channel. In the worst-case scenario, the mechanical effect could lead to the overall failure of a loess cover layer in a landfill. A new gas flow channel was formed between the rubber membrane and the loess specimen as a result of the interfacial effect. Although both the mechanical and interfacial effects can elevate the gas emission rate, the latter did not play a role in the improvement of the gas permeability; therefore, misleading interference took place in the evaluation of the gas permeability, and an overall failure of the loess cover layer. To tackle this problem, the point at which the large- and small-effective stress asymptotes cross on the volumetric deformation-P_eff diagram may be applied to give early warning signals of the potential overall failure of the loess cover layer in landfills in northwestern China.

Keywords: Gas breakthrough pressure; Gas permeability; Landfill cover; Loess; Mercury intrusion porosimetry.

MeSH terms

Air Pollutants* / analysis
Gases / analysis
Humans
Methane / analysis
Permeability
Refuse Disposal* / methods
Soil
Waste Disposal Facilities

Substances

Gases
Soil
Methane
Air Pollutants