西北地区黄土作为垃圾填埋场中间覆盖层的试验

垃圾填埋场中间覆盖层在垃圾分区或分层堆填作业过程中用于临时封闭垃圾堆体、控制降雨入渗并减少蚊蝇滋生和臭气等. 常用的高密度聚乙烯(high density polyethylene, HDPE)膜作为中间覆盖层, 存在易被垃圾刺穿导致坡面雨水大量入渗和造价较高等问题. 我国西北地区气候干旱且黄土分布广泛, 这些黄土是当地制作垃圾填埋场中间覆盖层非常便利的材料. 对黄土中间覆盖层的夯实施工、防渗性能和历经干湿循环作用后开裂导致其渗透系数增大、防渗性能劣化进行了试验研究. 结果表明: 黄土的饱和渗透系数随干密度增大而增大, 当干密度达到1.60 g/cm³时其渗透系数为10⁻⁷~10⁻⁶ cm/s, 防渗性能较好; 现场双套环原位实验测得黄土饱和渗透系数为8.37×10⁻⁸ cm/s, 较室内试验大1 倍左右; 黄土层历经自然干湿循环作用后易开裂, 有裂缝条件下其饱和入渗系数为1.18×10⁻⁶ cm/s, 比无裂缝条件下的增大了14 倍左右. 在增设15 cm 厚的保护植被土层后, 黄土的开裂情况得到明显抑制.

Experiments on loess as intermediate cover in landfills in northwest China

The functions of intermediate covering layer of landfill include temporary enclosure of garbage, control of rainfall infiltration, reducing mosquito breeding, etc. High density polyethylene (HDPE) film is easy to pierce to cause rain infiltration, but the cost is high. The northwest area of China is dry, with loess widely distributed. It is convenient to be used as a landfill intermediate cover. Experimental studies are carried out on tamping construction, impervious performance and impervious performance deterioration after wetting and drying cycles. The results show that the saturated permeability coefficient of loess increases with increasing dry density. Dry density reaches 1.60 g/cm³ when its permeability is from 10⁻⁷ cm/s to 10⁻⁶ cm/s. The field double ring in situ experimental permeability coefficient is 8.37×10⁻⁸ cm/s, about double as in the indoor test. With the natural drying wetting cycle condition of saturated infiltration coefficient being 1.18×10⁻⁶ cm/s, it is 14 times greater than the condition without crack. Adding a soil vegetation layer with thickness of 15 cm, cracking of loess is suppressed.