Abstract Geosynthetic clay liners (GCLs) are widely used in landfill and heap-leach facility cover system for mitigating rainfall infiltration and gas migration into atmosphere. Laboratory tests were conducted to investigate methane diffusion and advection through GCLs. Gas permeability coefficient of GCL for the case with moisture content = 47.5% is one and two orders of magnitude greater than the cases with moisture content = 68.5% and 80.9%, respectively, when 20 kPa vertical stress was applied. The batch adsorption tests indicated that adsorption of methane onto bentonite is negligible. The concentration variation for the adsorption of methane onto bentonite can be neglected. However, methane concentration decreased by 14.2% for the test of methane adsorption onto GCL during the first 2–3 days. This is because methane was adsorbed by the geotextiles rather than by the bentonite in GCL. The large porosity and surface area of geotextiles provide lots of micropores for methane adsorption. Analytical model was then developed to analyze the performance of GCL-based liners system with respect to methane transport. The results indicate that methane emission fluxes for the case with SL + GCL are 7.8 and 5.1 times less than the cases with SL + CCL when the moisture contents were 25.9% and 35.1%, respectively. The methane emission fluxes for both of the SL + GCL and SL + CCL can be neglected when they are fully saturated. GCL is recommended to be used in arid and semi-arid regions rather than CCL. GCL is recommended to be used in arid and semi-arid areas rather than CCL. Advection plays a more important role in methane migration through SL + GCL and SL + CCL than that of diffusion. With moisture contents = 25.9% and 32%, methane emission flux attributed to advection accounts for more than 90% of the total emission flux for both cases of SL + GCL and SL + CCL. With the increase of moisture content of SL, the effectiveness of SL in reducing methane emission increases. The saved space for using GCL + SL composite cover compared with using a single SL cover is 0.7 m when the moisture content equals 25.9%, which is 0.5 m greater than the case when moisture content equals 32%. GMB plays a dominant role in inhibiting methane migration and reducing methane emission flux. When moisture content equals 25.9%, the methane emission fluxes for SL + GMB + GCL and SL + GMB + CCL are 343 times and 2643 times less than the cases with SL + GCL and SL + CCL, respectively.

中文翻译：

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土工合成粘土衬垫中甲烷对流扩散的实验研究

摘要 土工合成粘土衬垫（GCLs）广泛用于垃圾填埋场和堆浸设施覆盖系统，以减少降雨入渗和气体迁移到大气中。进行了实验室测试以研究通过 GCL 的甲烷扩散和平流。当施加20 kPa垂直应力时，GCL在水分含量= 47.5%的情况下的气体渗透系数分别比水分含量= 68.5%和80.9%的情况大一个和两个数量级。批量吸附试验表明，甲烷对膨润土的吸附可以忽略不计。甲烷吸附在膨润土上的浓度变化可以忽略不计。然而，在前 2-3 天，甲烷浓度降低了 14.2%，用于测试 GCL 上的甲烷吸附。这是因为甲烷被土工布吸附而不是被 GCL 中的膨润土吸附。土工布的大孔隙率和表面积为甲烷吸附提供了大量微孔。然后开发了分析模型来分析基于 GCL 的衬管系统在甲烷传输方面的性能。结果表明，当水分含量分别为 25.9% 和 35.1% 时，SL + GCL 情况下的甲烷排放通量比 SL + CCL 情况小 7.8 倍和 5.1 倍。SL + GCL 和 SL + CCL 的甲烷排放通量在完全饱和时可以忽略。建议在干旱和半干旱地区使用 GCL 而不是 CCL。建议在干旱和半干旱地区使用 GCL 而不是 CCL。与扩散相比，平流在通过 SL+GCL 和 SL+CCL 的甲烷迁移中起着更重要的作用。水分含量分别为 25.9% 和 32% 时，在 SL+GCL 和 SL+CCL 两种情况下，归因于平流的甲烷排放通量均占总排放通量的 90% 以上。随着SL水分含量的增加，SL减少甲烷排放的有效性增加。当含水率为25.9%时，使用GCL+SL复合盖板与使用单个SL盖板相比节省的空间为0.7m，比含水率为32%的情况大0.5m。GMB在抑制甲烷迁移和减少甲烷排放通量方面起主导作用。当水分含量为 25.9% 时，