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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 m2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。
Loess is widely distributed in northwestern China and is the main material of the top landfill cover of the local landfill. The gas permeation characteristics of the loess directly affects the control effect of overburden on landfill gas release. Using dialysis technology and self-made gas permeability coefficient measuring device, the variation of service moisture content of covered loess and its influence on gas permeability coefficient under dry and wet weather conditions were simulated and tested. And one of the landfill gas in rubbish body and cover was established Dimensional steady-state migration model. The effects of gas permeability coefficient and gas extraction rate of overburden on the control effect of landfill gas release were analyzed. The results show that the dialysis technology can effectively simulate the change of moisture content of covered loess, the gas permeability coefficient of compacted loess samples is on the order of 10-17 ~ 10-12 m2, and decreases with the increase of service moisture content, Loess with higher degree of compaction reduces more obviously; landfill gas pressure at the bottom of cover layer increases with the decrease of gas permeability coefficient. By means of negative pressure pumping of gas diffusion layer in the lower part of cover layer, coverage can be effectively reduced Layer bottom gas pressure and landfill gas release.