Abstract：The Gaomiaozi bentonite(GMZ001 Bentonite) from Inner Mongolia was mixed with quartz sand at different sand mixing ratios of 0%，10%，20%，30%，40% and 50%. The soil specimens were prepared by compacting the mixtures under a pressure of 20 MPa using an electronic compression press. The permeability coefficient and the swelling volume of the mixtures under confining pressure of 300 kPa were determined using a flexible-wall permeameter. Test results show that there is no significant change in permeability coefficient of GMZ001 bentonite-quartz sand mixtures within the sand mixing ratios ranging from 0% to 50%. These mixtures can therefore meet the requirement of impermeability for backfill/buffer materials. In order to better understand the influence of sand mixing ratio and dry density on the permeability coefficient，the effective clay dry density (ECDD) is adopted. It can be seen that there was a good linear-attenuation relationship between the logarithm value of permeability coefficient and ECDD of bentonite-sand mixtures. Based on the results of compaction test，it can be proved that the permeability coefficient of GMZ001 bentonite-sand mixtures is a single-value function of sand mixing ratio. Thereby，the permeability coefficient of GMZ001 bentonite-sand mixtures can be predicted by the function under different mixture compaction conditions，hoping that this result could provide a theory basis for the optimization and design of the bentonite-quartz sand as buffer/backfill materials.
2011, Vol. 30 
