Hydro-mechanical behaviour of compacted bentonite-sand mixture used as sealing materials in radioactive waste disposal

In order to verify of the geological high-level radioactive waste disposal, IRSN has undertaken the SEALEX research project to control the long-term performance of swelling clay-based sealing systems. Compacted bentonite-sand mixtures are one of the most appropriate sealing materials studied in this project because of its low permeability and good swelling capacity. Once installed, this material will be in contact with the host-rock pore water and start swelling to close all the gaps in the system (internal pores, rock fractures and technological voids) and then, swelling pressure develops. In parallel with the in-situ SEALEX project, laboratory experiments are performed to investigate the sealing properties under this complex hydro-mechanical condition taking into consideration the effect of technological voids. In this work, two approaches for this study are presented : one studies the sealing properties of the buffer as a homogeneous material, while the second distinguishes two states of the material : the compacted central part and the loose gel formation in the technological void following swelling