Decoding Methane Flow in Fractured Clay: A Semi-Analytical Model With Matrix Diffusion and Advection

IF 3.4 2区 工程技术 Q2 ENGINEERING, GEOLOGICAL International Journal for Numerical and Analytical Methods in Geomechanics Pub Date : 2024-09-27 DOI:10.1002/nag.3853
Qiao Wang, Fusheng Zha, Hamid Rajabi, Long Xu, Huaxiang Yan
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Abstract

Landfills emissions, ranking as the third-largest anthropogenic source of methane in the atmosphere, pose environmental challenges and threaten public health. The pivotal role of clay as a mitigating agent for methane emission within landfill cover systems cannot be overstated; however, our understanding of methane escape from fractured clay remains limited. This study aims to address the existing gaps by proposing a robust analytical model of methane transport in both fractures and clay matrix. Our investigation also includes a dimensionless analysis to govern the relative significance of diffusion and advection in methane emission from fractured clay, systematically reviewing factors such as the degree of water saturation (Sr) and fracture width. The methane concentration profiles in cracked clay demonstrated escalating sensitivity to Péclet (Pe) numbers, especially when advection dominates transport. Our findings also highlight the prevalence of preferential methane flow with increasing Sr in the clay matrix. The flux of methane emission from fractures at Sr = 0.8 was 130 times greater than that from intact clay. However, the study necessitates considering methane emission from clay matrix, particularly in dry clay conditions (Sr = 0.2 and 0.4). The accumulated methane emission flux from intact clay, more than that emitted from fractures by about 2.5 times at Sr = 0.2, was 1.3 × 10−5 g/m/s. The findings significantly advance the understanding of gas transport in fractured geomaterials, revealing the effect of water saturation and crack width on methane emissions from fractures. Overall, the outcomes emphasize the inclusion importance of methane emission from cracked clay in the design of gas barriers.

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解码甲烷在断裂粘土中的流动:基质扩散和平流半解析模型
垃圾填埋场排放的甲烷是大气中第三大人为来源,对环境构成挑战,并威胁着公众健康。在垃圾填埋场覆盖系统中,粘土作为甲烷排放的缓解剂,其关键作用怎么强调都不为过;然而,我们对甲烷从断裂粘土中逸出的了解仍然有限。本研究旨在通过提出一个可靠的甲烷在裂缝和粘土基质中迁移的分析模型来弥补现有的不足。我们的研究还包括一项无量纲分析,以确定甲烷从裂缝粘土中排放时扩散和平流的相对重要性,并系统地审查了水饱和度(Sr)和裂缝宽度等因素。裂缝粘土中的甲烷浓度剖面显示出对佩克莱特(Pe)数的敏感性不断上升,尤其是当平流在传输中占主导地位时。我们的研究结果还突出表明,随着粘土基质中 Sr 的增加,甲烷会优先流动。当 Sr = 0.8 时,从裂缝中排放的甲烷流量比从完整粘土中排放的甲烷流量大 130 倍。不过,这项研究有必要考虑粘土基质的甲烷排放,尤其是在干燥粘土条件下(Sr = 0.2 和 0.4)。在 Sr = 0.2 时,完整粘土的甲烷累积排放通量为 1.3 × 10-5 g/m/s,是裂缝排放通量的约 2.5 倍。研究结果极大地推动了对断裂土工材料中气体传输的理解,揭示了水饱和度和裂缝宽度对裂缝甲烷排放的影响。总之,研究结果强调了在设计气体屏障时将裂缝粘土中的甲烷排放纳入其中的重要性。
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来源期刊
CiteScore
6.40
自引率
12.50%
发文量
160
审稿时长
9 months
期刊介绍: The journal welcomes manuscripts that substantially contribute to the understanding of the complex mechanical behaviour of geomaterials (soils, rocks, concrete, ice, snow, and powders), through innovative experimental techniques, and/or through the development of novel numerical or hybrid experimental/numerical modelling concepts in geomechanics. Topics of interest include instabilities and localization, interface and surface phenomena, fracture and failure, multi-physics and other time-dependent phenomena, micromechanics and multi-scale methods, and inverse analysis and stochastic methods. Papers related to energy and environmental issues are particularly welcome. The illustration of the proposed methods and techniques to engineering problems is encouraged. However, manuscripts dealing with applications of existing methods, or proposing incremental improvements to existing methods – in particular marginal extensions of existing analytical solutions or numerical methods – will not be considered for review.
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