Effects of technological voids and hydration time on the hydro-mechanical behaviour of compacted bentonite/claystone mixture

Pre-compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been considered as a promising sealing/backfilling material in deep geological repository for high-level radioactive waste France. When the pre-compacted blocks are emplaced gallery, technological voids can remain. After infiltration of groundwater from host rock, they will swell freely, filling voids, and then undergo further hydration under constant-volume conditions. From perspective storage safety, it is essential to understand effects time on hydro-mechanical behaviour such blocks. In this work, series tests at various times was carried out compacted bentonite/COx with different voids. The evolutions swelling pressures axial radial directions well hydraulic conductivity were monitored while wetting. predetermined times, dry density, water content suction positions determined, together microstructure investigation using mercury intrusion porosimetry. It observed that soils close initial swelled filled upon contact water, significant increases large-pore medium-pore void ratios. variation density profile time, compression zones could be identified: zone, corresponding subjected compression, decrease ratios over whereas higher than expected final one underwent swelling, ratio increasing until saturation slight due redistribution soil. Owing soil heterogeneity, pressure samples slightly larger those without voids; contrarily, lower