In high-level radioactive waste(HLW) repository

buffer backfilling material should be pre-compacted to a certain density. The compression properties of buffer backfilling material have an important influence on the safety design

construction and operation for geological HLW repository. At present

bentonite-sand mixtures are considered to be the ideal buffer backfilling material in the geological HLW repository in China. the compression properties of bentonite-sand mixtures with different dry densities and sand ratios

whose water content is constant

are performed by WG oedometer. It is found that the compression coefficient a1-2 decreases quadratically with the increase of dry density

but it increases nonlinearly with the increase of sand ratio. Based on the concepts of effective clay density and effective water content

we try to explain the changes of the compression coefficient a1-2 with dry density and sand ratio. The regression analysis model of bentonite-sand mixtures with various dry densities and sand ratios are fitted based on the experimental data

and it hopes that this result can be used to provide a related basis of the optimization of buffer backfilling material.