Evaluation of cementation effects on swelling properties of bentonite buffer material using natural analogue

Bentonite buffer material designed for the geological disposal of high-level radioactive waste must maintain its swelling capacity for tens of thousands of years in a disposal environment. During such a long period, a salient concern is that the designed functions might degrade because of cementation in the buffer. For this study, to estimate cementation effects on buffer swelling properties, bentonite ore was tested as a simulant: a natural analogue of the cemented buffer. This natural system resembling a geologic repository provides evidence of some inaccessible features such as long-term and structural complexity. Swelling pressure and swelling deformation tests conducted under different confining conditions were used to assess ore blocks (i.e., undisturbed specimens) and crushed ore (i.e., reconstituted specimens). The test results indicate a unique relation between the specimens’ confining pressure and their dry density conditions for undisturbed and reconstituted specimens. These unique relations elucidated the extent of cementation effects on the designed functions of the buffer material.