Predicting hydraulic conductivity of bentonite backfill after swelling

Mixtures of sand and bentonite will be used as bentonite-based backfills for radioactive waste repositories in Japan. Very low hydraulic conductivity of the sand-bentonite mixtures is expected to keep wastes separated from the surrounding environment. However, the function of low permeability of bentonite-based backfills is degraded by the altered hydraulic conductivity of sand-bentonite mixtures after swelling deformation. This study investigates experimentally hydraulic conductivity changes before and after swelling for sand-bentonite mixtures. Furthermore, results confirm the applicability of theoretical equations for evaluating the hydraulic conductivity of bentonite-based materials, which have already been proposed in Komine (2008), by comparing calculated results and experimental results.