混合重金属离子侵蚀饱和黏性土渗透特性试验研究

渗透特性是表征黏性土层防渗能力及防污性能的关键控制因素，黏土衬垫渗透系数的正确选择对保证垫层的防污效果具有极其重要的意义。采用柔性壁渗透仪，通过室内试验研究了混合重金属离子共存情况下侵蚀饱和黏性土的渗透特性变化规律。试验结果表明，将可溶性铜、铬离子混合与铜、锰离子混合溶液作为渗液，黏性土渗透性均随着掺入离子浓度比例的增大而逐渐增强，且相同试验条件下，铜、铬离子混合溶液作为渗液测得的黏土渗透系数值大于铜、锰离子混合溶液作为渗液测得的渗透系数值。混合重金属离子的存在削弱了黏土垫层作为工程防污屏障服役的能力，并对黏土层的水力传导性起到了劣化作用。试验土样微观结构分析表明，渗液特性的改变影响了土样内部的微观结构，随着渗液混合离子质量比的增大，土样中出现了凝聚体且有效输运孔隙通道增大，与宏观渗透特性的变化规律相吻合。研究结果能够为有效评估黏土防污屏障的防渗隔污能力及研究堆场渗液在黏土垫层中的运移机制提供参考。

Permeability of saturated clay eroded by mixed heavy metal ions

Permeability is the key control factor representing anti-seepage ability and anti-fouling property of clay layer, and the proper choice of permeability coefficient of clay liner is crucial to ensure anti-fouling effect of the liner. The purpose of this investigation is to characterize the variation of the permeability of saturated clay with mixed heavy metal ions solution as permeant fluid. The permeability tests are performed with flexible-wall permeameters. It is shown that the permeability of saturated clay is enhanced with the increase in proportion of ions concentration for the permeant fluid with soluble Cu2+ and Cr3+, Cu2+ and Mn2+. In addition, under the same experiment conditions, the permeability coefficient of clay liner permeated with Cu2+ and Cr3+ mixable solution is larger than that with Cu2+ and Mn2+ mixable solution; the existence of mixed heavy metal ions weakens the ability of clay liner, and deteriorates the hydraulic conductivity of clay layer. The scanning electron microscope reveals that the permeant fluid plays an important role in changing the soil microstructure. The effective transport pore fluid passage increases with increasing mass ratio of mixable ions in permeant fluid, and aggregates are found in the soil samples, which is in good agreement with variation of macroscopic permeability. The results can provide a reference for evaluating anti-fouling ability of clay as valid barrier.