Influence of initial water content on the swelling behaviors of bentonite-sand mixtures

• 1、Geological Department, State Key Laboratory of Continental Dynamics, Xi’an 710069, China

Abstract：The compaction tests on the GMZ bentonite–sand mixtures as backfill/buffer material were conducted and the influence of initial water content on the swelling behaviors were investigated in this paper. The sand addition ratios of the bentonite–sand mixtures are 0%, 10%, 20%, 30%, 40% and 50%, and initial water contents varied from 5% to 45%. The samples of bentonite-sand mixtures for swelling tests were prepared with various initial dry densities, ranging from 1.30 g/cm3 to 1.90 g/cm3. The laboratory tests indicate that, with the increase of initial water content, the swelling speed for both swelling pressure test and swelling strain test are slowed in the primary stage, The maximum swelling pressure is decreased with the increase of the initial water content in the lower water content range, and remained almost constant in the higher water content range. The effect of initial water content on the maximum swelling pressure is higher with the increase of initial dry density, while it is lower with the increase of sand content ratio. The maximum swelling strain is linearly reduced with the increase of initial water content, and the effect is also lower for samples of lower dry densities and higher sand content ratios.

Keywords： High-level radioactive waste geological disposal backfill material bentonite–sand mixture initial water content swelling behavior