溶液特征对石屑掺膨润土混合土的渗透特性影响

Influences of solution characteristics on permeability of stone-bentonite mixtures

垃圾填埋是目前世界各地处置城市固废的主要方法,为了有效防止渗滤液污染地下水和周边环境,在垃圾填埋场底部铺设含黏土或膨润土掺砂混合土的防渗系统。利用采石场的石屑和膨润土配制防渗材料,通过渗透试验、Zeta电位试验和X射线衍射试验,分析溶液种类和浓度对渗透特性的影响机理。研究结果表明随着离子浓度的增大,混合土的渗透系数变大,其主要是由于溶液中的离子与钠基膨润土进行离子交换,膨润土土粒间斥力与土粒双电层厚度减小,且膨润土中的蒙脱石层晶间距增大。

Landfill is the main method for disposaling the municipal solid waste in cities around the world.In order to effectively protect the underlying ground-water resources and surrounding environments from leachate,the bottom of landfills is lined with impervious system.The compacted clay or bentonite-sand mixtures are the widely-used materials for impervious system.In this study,the impervious materials are prepared by stone chips of a quarry and bentonite.The influence mechanism of solution characteristics on permeability is analyzed through permeation tests,Zeta potential and X-ray diffraction.The results show that the permeability of stone-bentonite mixtures become larger with the increase of the ion concentration,which is mainly due to the exchange of ions in solution with sodium bentonite,the reducement of the repulsion between soil particles and the thickness of the electric double layer,and the increase of the crystal spacing of the montmorillonite layer in the bentonite.