Abstract: 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.

Key words: Al-OM flocs, anti-seepage, slurry concentration, injection speed, particle-size distribution