A New Method for Determination of the Final Swelling Strain of Sand-Bentonite Mixtures

Abstract

In the deep geological disposal of high-level radioactive waste, accurately determining the swelling strain of bentonite-based material is essential for barrier design and numerous studies have conducted swelling deformation tests to investigate the swelling characteristics of bentonite. However, as it usually takes a long period of time for the swelling deformation to converge, there is no clear criterion for determining when to terminate the experiment, and the test duration varies among studies. Thus, in this study, one-dimensional swelling deformation tests with low confining pressure (19.6 kPa) were conducted for a long duration and the effect of approximation data range on the approximation of final swelling strain using hyperbola was evaluated. With the obtained time histories, a method to calculate the final swelling strain which is less dependent on approximation data range was discussed. Finally, a method to determine the experimental duration from bentonite dry density was proposed.