An experimental study on diffusion characteristics of hardened liner materials to inorganic chemicals

For materials of very low hydraulic conductivity used in the landfill liner systems, e.g., natural clay liners, soil-cement liners, etc., diffusion characteristics should be evaluated, as the transport mechanism of contaminant through them is diffusion controlled. Studies on the diffusion characteristics of the hardened liner materials, such as the soil cement, are relatively few compared with those of clayey soils. In this paper, diffusive characteristics of hardened liner materials (HLMs) applied to the liner system of Sudokwon Metropolitan Landfill in Korea, were studied. Laboratory pure diffusion column tests in the pure- and the advection-diffusion status were performed for the chemicals, NaCl, KCl, and CaCl₂. To evaluate the diffusion coefficient of a HLMs system, a one-dimensional numerical transport program was developed for use in a multi-layered HLMs system. The range of dispersion coefficients of advection diffusion column tests was a little narrower than that of diffusion coefficients of pure diffusion tests, although the two coefficients were quite close. The effective diffusion coefficients of chloride ions of a HLMs were about a half of those in clayey soil due to the high density by compaction and curing. Diffusion coefficients of chloride ions in this study were correlated closely with hydraulic conductivities of the materials tested and were consistent with work in the literature.