利用铝-有机质絮状物降低渗透系数的试验研究

Experimental study of hydraulic conductivity reduction induced by Al-OM flocs-clogging

防渗对堤坝等水利工程、地下工程和污染物迁移都具有重要意义。基于自然灰化土层形成过程中因金属离子和有机质络合反应形成不透水土层的过程,提出了利用六水合氯化铝(AlCl3·6H2O)和有机质(OM)相互反应生成Al-OM絮状物来降低渗透系数的方法。开展了系列的注入试验,探究了浆液浓度、注浆速度和砂土颗粒级配对渗透系数降低和形成屏障长度的影响。研究结果表明:该方法可以有效地降低砂土的渗透性;渗透系数降低的速度随着浆液中Al-OM絮状物浓度的增大而增加;由于絮状物浓度的增加,孔隙堵塞的速度增快,从而阻止了其继续扩散,形成的屏障长度随之减小;Al-OM絮状物的尺寸随注浆速度的增大而减小。当注浆速度较大时,Al-OM絮状物的尺寸较小,因此渗透系数降低慢而扩散距离远。砂土的颗粒级配对渗透系数降低有重要影响,粗颗粒含量越大,渗透系数降低越小。

Anti-seepage is of great significance on hydraulic engineering such as dikes, underground engineering and pollutant migration. Based on the formation of impermeable soil layers due to the complexation between metal ions and organic matter during the formation of natural podzolic soil layer, a novel approach was proposed to reduce soil permeability by Al-OM flocs formed by the interaction between aluminum chloride(AlCl3·6H2O) and organic matter(OM). Extensive laboratory tests were conducted to investigate the effects of slurry concentration, injection rate and the particle size distribution of sand on the reduction of hydraulic conductivity and the distance of flow barrier. The results showed that the Al-OM flocs could significantly reduce the soil permeability. As the concentration of Al-OM flocs in the slurry increased, the decreasing rate of hydraulic conductivity also increased. This is because due to the increase in the concentration of Al-OM flocs, the rate of pore clogging increased, which prevented it from diffusing further, thus reduced the length of flow barrier. The size of Al-OM flocs decreased with the increasing injection rate. When the injection rate was larger, the size of Al-OM flocs was small, so the reduction of hydraulic conductivity was slower and the diffusion distance of Al-OM flocs was longer. The particle size distribution of sand had a significant impact on the reduction of hydraulic conductivity. The higher the coarse particle content was, the slower the reduction of hydraulic conductivity was.