Abstract: 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.

Key words: permeability, mixed ions, clay liner, anti-fouling barrier