This paper is focused on chemical diffusion parameters of soil-bentonite mixture which is one of barrier materials commonly used for containment of ground contamination. Although vertical cutoff walls using low-permeable materials, such as soil-bentonite mixture, need to prevent mobile contaminants from migrating in the aquifer for a long period, a limited number of studies have focused on chemical diffusion through hydraulic barriers, whereas factors affecting hydraulic conductivity of barrier

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... materials have been frequently discussed. In this study, solute transport through soilbentonite mixtures made with a bentonite powder content of 50 kg/m 3 was evaluated by a laboratory experiment using an acrylic vertical column and a one-dimensional advection-dispersion finite element analysis. Two soils having different particle size distributions were used as parent soil. By fitting experimental and numerical results regarding the chloride flux, effective diffusion coefficient, De, and effective porosity, ne, of the mixtures were determined with two significant digits. Results obtained in this study indicate that soil-bentonite mixtures made with a same bentonite powder content can have a similar De value, regardless of the type of parent soil. Another important finding is that larger total porosity of mixtures led to smaller ne value probably because powder bentonite can sufficiently hydrate and swell in macropores of the mixture with a larger total porosity; therefore, pore structure of bentonite became more dominant for that of soilbentonite mixture.