摘要
黄土在我国西北地区广泛分布,是当地垃圾填埋场封顶覆盖层的主要材料,该材料的气体渗透特性直接影响了覆盖层对填埋气释放的控制效果。利用渗析技术和自制的气体渗透系数测量装置,模拟和测试了干湿气象条件下覆盖黄土服役含水率变化及其对气体渗透系数的影响,并建立填埋气在垃圾体和覆盖层中的一维稳态运移模型,分析了覆盖层气体渗透系数和抽气速率对填埋气释放控制效果的影响。研究结果表明：渗析技术能有效模拟覆盖黄土服役含水率的变化,压实黄土试样的气体渗透系数介于10^-17-10^-12 m^2量级,随服役含水率的增加而降低,且对于压实度比较高的黄土降低得更加明显;覆盖层底部的填埋气压随气体渗透系数的减小而增大,通过覆盖层下部的气体扩散层负压抽气等措施,可有效减小覆盖层底部气压和填埋气的释放量。
In Northwest China, loess is widely distributed and is the main material for landfill final cover. The gas permeability of loess will effect the landfill gas emission directly. In order to study the effect of the water content on the gas permeability characteristics of the loess cover in service, a device is developed to measure the gas permeability of unsaturated compacted loess specimens. The water content of the specimens after compaction is controlled using the osmotic technique. In addition, a one-dimensional steady-state model of gas migration in waste layers and final cover is established on the basis of the flow theory in porous media. The effects of gas permeability of the loess cover and gas extraction rate in the diffusion layer on landfill gas emission are investigated. The experiments demonstrate that the osmotic technique can effectively simulate the changing service water content of the loess cover. The measured gas permeability of loess specimens ranges from 10-17 m2 to 10-12 m2, and decreases with the increase of service water content; and the decrease is more significant for the high density specimens. The gas pressure at the bottom of the loess cover increases with the decrease of the gas permeability. Extracting landfill gas from the gas diffusion layer of the cover is able to reduce the gas pressure and the landfill gas emission rate.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2015年第7期1973-1980,共8页
Rock and Soil Mechanics
基金
国家重点基础研究发展计划(973计划)(No.2012CB719805)
