柔性垂直防渗技术膨润土-黏土密封材料防渗性能研究

以长沙某厂区内天然黏土为主要原料，采用水溶液聚合法，在室温条件下，通过聚丙烯酰胺改性膨润土与黏土混合，制备密封材料，用于柔性垂直防渗墙建设工程底部区域密封，以防止地下水从高密度聚乙烯(HDPE)土工膜底绕流。通过室内试验研究3种不同改性剂以及膨润土添加量对密封材料渗透系数的影响以及密封材料对六价铬的阻滞吸附作用。结果表明：聚丙烯酰胺改性膨润土能够减小密封材料的渗透系数，而羟丙基甲基纤维和聚乙烯醇在一定程度上导致密封材料渗透系数增大；随着改性膨润土掺入量的增加，密封材料的渗透系数逐渐减小。在模拟柱迁移试验中，密封材料对污染物的截留率可达68.5%。基于长沙某柔性垂直防渗墙工程，对建成防渗墙区域进行示踪剂弥散迁移试验，在下游接收井中均未检测到示踪剂，说明该密封材料在工程应用上能有效防止底部地下水绕流。

Research on the impermeability of the bentonite-clay sealing materials in the flexible vertical impermeability technology

Taking the natural clay in an enterprise in Changsha as the main raw materials, using the experiment method of water solution polymerization at the room temperature, a new type of sealing material was prepared by mixing bentonite and clay modified with polyacrylamide (PAM), which was used to seal the bottom area of flexible vertical impervious wall construction projects to prevent the groundwater from flowing around the bottom of the high-density polyethylene (HDPE) geomembrane. The influence of three different modifiers and the amount of bentonite on the permeability coefficient of the sealing material and the blocking and adsorption of hexavalent chromium were studied by laboratory experiments. The results showed that the permeability coefficient of the sealing material could be reduced when the bentonite was modified with PAM, while, to a certain extent, the hydroxypropyl methyl fiber and polyvinyl alcohol increased the permeability coefficient of the sealing material. With the increase of the amount of modified bentonite added, the permeability coefficient of the sealing material decreased gradually. In the simulated column migration experiment, the retention effect of the sealing material on pollutants could reach 68.5%. Based on a flexible vertical impermeability wall project in Changsha, no tracer was detected in the downstream receiving well in the tracer dispersion and migration experiment on the area of the built impermeability wall, indicating that the sealing material could effectively prevent groundwater from flowing around the bottom on the engineering application.