Predicting swelling characteristics of bentonites

Bentonite is currently planned for use as a buffer and backfill material for repositories of high-level nuclear waste because these materials must have swelling characteristics to seal the waste. However, it is necessary to choose the appropriate bentonite from among many kinds of bentonite in the design of buffer and backfill materials. To do this, the writers have proposed a new prediction method for swelling characteristics of bentonite-based buffer material. This prediction method comprises some equations that were previously developed for repulsive and attractive forces between two montmorillonite layers; others included in the method are the writers' previously proposed equations for (1) the swelling volumetric strain of montmorillonite (Komine and Ogata 1999), and (2) the influence of pore water chemistry and specific surface of bentonite (Komine and Ogata 1996a). However, the applicability of this prediction method to swelling characteristics of some bentonites remains unclarified. This study clarifies the applicability of the prediction method by comparing predicted results with experimental data for five kinds of bentonite produced in Japan and the United States.