生物炭调节黏土覆盖层的渗透特性及其影响机制

Permeability characteristics of clay overburden regulated by biochar and its influence mechanism

为研究生物炭掺量和粒径对生物炭-黏土混合土渗透特性的影响,采用自主研发的柔性壁水-气联合渗透仪,获得了不同生物炭掺量(0,5%,10%,15%和20%)、不同粒径范围(>74,>40~74和20~40μm)生物炭-黏土混合土的饱和渗透系数.试验结果表明:随着生物炭掺量增加,饱和渗透系数k sat均表现不同程度增大;随着干密度增加,k sat逐渐减小,并且随着生物炭掺量增加,这种减小趋势越明显.当生物炭粒径大于74μm时,生物炭-黏土混合土的渗透系数增大.同时,结合核磁共振(NMR)试验结果分析了土样孔隙结构的变化规律,从微观层面解释了生物炭-黏土混合土饱和渗透系数增加的原因.研究结果可为填埋场生物炭改性黏土最终覆盖层的设计和施工提供生物炭掺量和粒径选取的参考依据.

In order to study the effect of biochar content and particle size on the permeability behavior of biochar-clay mixture,the saturated permeability coefficient was obtained for biochar-clay mixture with different biochar contents(0,5%,10%,15%,and 20%)and particle sizes(>40-74,20-40,and>74μm)by using the self-developed flexible wall water air combined permeability instrument.The experimental results demonstrate that the saturated permeability coefficient increases in varying degrees with the increase of biochar content.With the increase of dry density,the saturated permeability coefficient decreases gradually,and the decreasing trend is more obvious with the increase of biochar content.When the particle size of biochar is greater than 74μm,the permeability coefficient of the biochar-clay mixture increases.At the same time,combined with the results of the nuclear magnetic resonance(NMR)test,the change law of samples pore structure was analyzed,and the reason for the increase of saturated permeability coefficient of the biochar-clay mixture was explained from the micro level.The research results can provide a reference for the selection of biochar content and particle size in the design and construction of the landfills′final biochar-amended clay cover.