生物炭改性填埋场覆盖层土的渗气特性研究

doi:10.13722/j.cnki.jrme.2022.0041

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摘要生物炭具有多孔结构、高比表面积和强吸附特性。在填埋场传统黏土覆盖层中添加生物炭制成生物炭改性黏土覆盖层，实现生物削减填埋场逸出甲烷的目的。添加生物炭可改变土体的孔隙结构，改善土体中气体的流动性，但对填埋场覆盖层气体流动特性的影响机制尚不清楚。因此，以生物炭–黏土混合土的渗气特性为主要评价指标，探讨生物炭掺量和粒径对生物炭–黏土混合土渗气特性的影响规律与机制。采用研发的柔性壁气相渗透测试装置，测定不同生物炭掺量、不同生物炭粒径组的生物炭–黏土混合土的气体渗透系数，并结合核磁共振技术分析土体孔径分布的变化规律。研究结果表明：对于干密度不小于90%黏土最大干密度的生物炭–黏土混合土，存在一生物炭最优掺量，其气体渗透系数达到最低。当生物炭掺量小于该最优值时，气体渗透系数随生物炭掺量的增大而减小，该趋势在较低干密度时更加明显；当大于该最优生物炭掺量时，气体渗透系数随生物炭掺量的增大逐渐增大。对比无交集粒径组生物炭与黏土混合土的气体渗透系数可得，随着生物炭粒径的减小，气体渗透系数逐渐降低。利用NMR微观测试结果解释生物炭–黏土混合土的气体渗透系数在特定条件下随生物炭掺量和粒径的增大而增大的变化机制。该研究可为填埋场生物炭改性黏土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。

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	李明玉1
	孙文静2

关键词 ：土力学, 生物炭–黏土混合土, 掺量, 粒径, 渗气特性, 核磁共振, 孔径分布

Abstract：Biochar has a porous structure，higher specific surface area and stronger adsorption characteristics. Adding biochar to the traditional clay cover of landfill，i.e.，biochar-amended clay cover，so as to achieve the purpose of biologically reducing the methane released from the landfill. Adding biochar could change the pore structure of the soil and improve the air mobility in the soil, but the mechanism of influence on the air flow characteristics of the landfill cover is not clear. Therefore，the air permeability characteristics of biochar-clay mixed soil were used as the main evaluation indicators to explore the influence law and mechanism of biochar content and particle size on the air permeability characteristics of biochar-clay mixed soil. The air permeability coefficient ka of biochar-clay mixed soil with different biochar contents and different biochar particle size groups was measured by using the self-developed flexible wall air permeability testing device，and the changes of pore size distribution are analyzed by nuclear magnetic resonance(NMR) technique. The research results show that for the biochar-clay mixed soil whose dry density is not less than 90% of the maximum dry density of clay，there was an optimal biochar content，and its air permeability coefficient is the lowest. When the content of biochar is less than the optimal value，the air permeability coefficient decreases with the increase of the content of biochar, and the trend is more obvious at lower dry density. When the biochar content was larger than the optimal value，the air permeability coefficient gradually increases with the increase of the content of biochar. Comparing the air permeability coefficient of biochar-clay mixed soil with different biochar particle size groups without overlap，the permeability coefficient decreases with the decreased of biochar particle size. The NMR microscopic test results were used to explain the change mechanism of the air permeability coefficient of biochar-clay mixed soil increasing with the increase of biochar content and particle size under specific conditions. This study can provide a reference for the selection of biochar dosage and particle size for the design and construction of the final cover layer of biochar-amended clay in landfills.

Key words： soil mechanics biochar-clay mixed soil content particle size air permeability nuclear magnetic resonance pore size distribution

引用本文:

李明玉1，孙文静2. 生物炭改性填埋场覆盖层土的渗气特性研究[J]. 岩石力学与工程学报, 2022, 41(S2): 3543-3550.
LI Mingyu1，SUN Wenjing2. Gas permeability characteristics of biochar-amended landfill cover soil . , 2022, 41(S2): 3543-3550.

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http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2022.0041 或 http://rockmech.whrsm.ac.cn/CN/Y2022/V41/IS2/3543

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