Apparatus and Procedures for Assessing Inorganic Diffusion Coefficients for Geosynthetic Clay Liners

摘要

The apparatus and procedure for eprforming tests to obtain inorganic diffusion coefficients for Geosynthetic Clay Liners (GCLs) are described, and the processes (diffusion, anion exclusion and osmosis) that can affect the interpretation of these tests are discussed. Resuls from several inorganic diffusion tests on GCL and bentonite specimens show that the diffusion coefficients deduced for sodium (Na~+) and chloride (Cl~-) are directly related to the final bentonite void ratio. It is shown that diffusion through GCLs (or thin bentonite layers) can be modeled using a bulk porous media diffusion coefficient (D_p) consisting of the total porosity, n_t, and a deduced diffusion coefficient, D_t,(D_p-n_tD_t) without the need to establish he true effective diffusion coefficient (D_e)) and effective prosity (n_e). However, for a longer bentonite plug sample it is shown that the true effective diffusion coefficient (D_e) and effective porosity (n_e) must be established to predict the contaminant transport through the sample.