Abstract Reducing soil permeability by natural biopolymers, which absorb water to form viscous hydrated colloids, may sustainably improve earthen structures such as landfill covers. Previous studies mainly investigated biopolymer effects on water permeability of saturated soils. However, performance of biopolymers in unsaturated soil is unclear, especially for gas permeability. This study examined effects of two biopolymers on gas permeability of compacted clay at various soil densities and compaction water contents using a flexible wall permeameter. The density is represented by degree of compaction (DOC). Statistical analysis was also performed for the three replicates of 95% DOC. Soil microstructure was analyzed by mercury intrusion porosimetry (MIP) and scanning electronic microscopy (SEM). Results showed that gas permeability of clay with biopolymers was always lower than that of pure clay with reduction of up to two orders of magnitude. No significant difference was found in the performance between the two biopolymers for most conditions. This is consistent with the statistical results. Reducing gas permeability by biopolymers is due to the reduction in soil macro pores and pore clogging as evidenced by MIP and SEM results. For 75% and 85% DOC, the clay with and without biopolymers showed an increase in gas permeability as compaction water content increased. Until DOC reached 95%, only gas permeability of the clay with biopolymers decreased with an increasing water content since viscous biopolymers stick soil particles and reduce macro pores. Moreover, the permeability reduction by biopolymers was enhanced with an increasing water content as more water is available to hydrate biopolymers and thus facilitate pore clogging. Statistical analysis also supports that the influence of biopolymers becomes more significant with an increasing water content.

中文翻译：

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生物聚合物对不同密度和含水量压实粘土气体渗透率的影响

摘要 通过吸收水分形成粘性水合胶体的天然生物聚合物降低土壤渗透性，可以持续改善垃圾填埋场等土结构。以往的研究主要研究生物聚合物对饱和土壤透水性的影响。然而，生物聚合物在不饱和土壤中的性能尚不清楚，尤其是在透气性方面。本研究使用柔性壁渗透计检查了两种生物聚合物对不同土壤密度和压实水含量下压实粘土的透气性的影响。密度由压实度 (DOC) 表示。还对 95% DOC 的三个重复进行了统计分析。土壤微观结构通过压汞法（MIP）和扫描电子显微镜（SEM）进行分析。结果表明，含生物聚合物的粘土的透气性始终低于纯粘土，最多降低两个数量级。在大多数条件下，两种生物聚合物之间的性能没有显着差异。这与统计结果一致。MIP 和 SEM 结果证明，生物聚合物降低气体渗透性是由于土壤大孔隙和孔隙堵塞的减少。对于 75% 和 85% DOC，含和不含生物聚合物的粘土随着压实含水量的增加显示出气体渗透性的增加。直到 DOC 达到 95%，只有含生物聚合物的粘土的透气性随着含水量的增加而降低，因为粘性生物聚合物会粘附土壤颗粒并减少大孔。而且，生物聚合物的渗透性降低随着含水量的增加而增强，因为更多的水可用于水合生物聚合物，从而促进孔隙堵塞。统计分析也支持生物聚合物的影响随着水含量的增加而变得更加显着。