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目的:我国西北地区黄土分布广泛,黄土作为当地固废填埋场的覆盖土料具有广泛的应用前景。现场尺度测试压实黄土覆盖层的气相渗透系数,从而可用于评估其填埋气减排性能。方法:1.在西安固废填埋场建立压实黄土覆盖层试验基地(图2);2.在试验基地的膜内核心测试区域布置通气试验系统,包括空气压缩机、通气管网、气压测试装置、含水率测试装置、温度传感器和静态箱(图3,5~7);3.在覆盖层表面裸露时和植草后分别进行通气试验测试压实黄土覆盖层的气相渗透系数。结论:1.当饱和度低于85%时,干密度为1.45 Mg/m3压实黄土的气相渗透系数随含水率增加而降低,但并不明显;但是当饱和度高于85%时,气相渗透系数随含水率增加而显著减小;2.黄土层和碎石层之间的毛细阻滞作用使得上部黄土层储存更多水分,并显著降低其气相渗透系数,这有利于降低填埋气的排放;3.裸露条件下,当压实黄土的体积含水率从36%增加至46%时,其气相渗透系数从3.67×10-12 m2降低至5.73×10-14 m2;4.植草后压实黄土的气相渗透系数比裸露条件下小近一个数量级,这主要是因为植被根系占据了压实黄土的大孔隙;5.现场尺度的压实黄土气相渗透系数比室内试验的结果高1至2个数量级,这主要是因为现场所用黄土含有大的结团,结团会增加黄土的孔隙直径以及减小孔隙的曲折度。
Objective: Loess in Northwest China is widely distributed. Loess as a local solid waste landfill covers a wide range of applications. Field-scale tests of the gas permeability coefficient of compacted loess overlay can be used to evaluate the landfill gas emission reduction performance. Methods: 1. Establish a compacted loess overlay test base in Xi’an Solid Waste Landfill Site (Figure 2); 2. Arrange ventilation test system in the membrane inner core test area of the test base, including air compressor, ventilation pipe network, air pressure Test device, moisture content test device, temperature sensor and static box (Figure 3, 5 ~ 7); 3, the permeability of the compacted loess cover gas permeability coefficient test when the cover surface is exposed and after the grass is aerated. When the saturation is lower than 85%, the gas permeability coefficient of compacted loess with dry density of 1.45 Mg / m3 decreases with the increase of water content, but it is not obvious. However, when the saturation is higher than 85%, the gas phase The permeability coefficient decreases with the increase of water content.2. The capillary block between the loess layer and the gravel layer causes the upper loess layer to store more water and significantly reduce the gas permeability coefficient, which is beneficial to reduce the landfill gas ; 3. Under the bare conditions, when the volumetric water content of compacted loess increased from 36% to 46%, the permeability coefficient of gas phase decreased from 3.67 × 10-12 m2 to 5.73 × 10-14 m2; 4. After the grass was planted The gas permeability coefficient of compacted loess is nearly an order of magnitude lower than that of bare soil, which is mainly because the vegetation roots occupy the macropores of compacted loess. 5. The permeability coefficient of compacted loess gas on site is 1 to 2 orders of magnitude, mainly because the loess used in the site contains large agglomerations, which increase the pore diameter of the loess and reduce the tortuosity of the pores.