Abstract: The shrinkage characteristics of bentonite-sand mixtures have a significant impact on the long-term safety and stability of
HLW repositories. Taking Gaomiaozi (GMZ) bentonite-sand mixture as the research object and quartz sand as additive, the shrinkage
characteristics of the sample during drying and water loss at 0-50% sand mixing ratio are explored. The results show that: (1) The water
evaporation in the mixture is divided into the normal rate stage, the deceleration rate stage and the residual stage, and sand mixing ratio
has a significant effect on each evaporation stage. (2) For the bentonite-sand mixtures, the effect of sand mixing ratio on the shrinkage
limit is not significant, but the shrinkage strain decreases with the increase of sand mixing ratio. When the sand mixing ratio is greater
than 30%, the shrinkage coefficient of soil sample decreases with the increase of soil mixing ratio. (3) The diametral shrinkage is greater
than the axial shrinkage, showing obvious anisotropy. And the diametral shrinkage makes greater contribution to the volume shrinkage.
(4) With the increase of sand mixing ratio, the soil sample is more easily to enter the unsaturated state from the saturated one, and the
final void ratio also increases continuously

Key words: high-level radioactive waste, geological disposal, bentonite-sand mixtures, sand mixing ratio, drying shrinkage, shrinkage parameters