Unsaturated bentonite–sand mixtures (BSMs) are accepted generally as ideal buffer/backfill materials in geologic repositories because of its excellent performance. Water retention characteristics are the important factor that affect the engineering properties of BSMs, but little attention has been devoted to that of Gaomiaozi (GMZ) BSMs under controlled-temperature in high suction range. This study evaluated the soil–water characteristic curves (SWCCs) of compacted GMZ BSMs using the vapour equilibrium technique with different sand content and temperature under unconfined conditions. It was found that the sand grains size had a negligible effect on the SWCCs in the high suction range. As the temperature increased, the decreasing adsorption and the increasing evaporation capacity promoted the decrease of water content. The BSMs changed from the compact structure to a loose structure with increasing sand content, which strengthened the flow of vapour and evaporation of water from bentonite and leaded to an observable reduction of water retention characteristics of GMZ BSMs. We presented a new empirical equation for unsaturated BSMs in the high suction rang considering effects of temperature and sand content, and that processed the data more efficiently and described satisfactorily the effects of temperature and sand content on the SWCCs of GMZ BSMs.

由于其优异的性能，不饱和的膨润土-砂混合物（BSM）被普遍接受为地质储层中的理想缓冲/回填材料。保水特性是影响BSMs工程性能的重要因素，但在高吸力范围内的可控温度下，高庙子（GMZ）BSMs的关注很少。这项研究使用蒸汽平衡技术，在无限制条件下，采用不同含沙量和温度的方法，对压实的GMZ BSM的土壤-水特征曲线（SWCC）进行了评估。发现在高吸力范围内，沙粒尺寸对SWCC的影响可忽略不计。随着温度的升高，吸附量的减少和蒸发能力的增加促进了水含量的降低。BSM从紧凑的结构变为具有增加的砂含量的松散结构，这增强了膨润土的蒸汽流动和水的蒸发，并导致GMZ BSM的保水特性明显降低。考虑到温度和含沙量的影响，我们提出了一个新的经验公式，用于考虑高吸力范围内的非饱和BSM，并能更有效地处理数据，并令人满意地描述了温度和含沙量对GMZ BSMs SWCC的影响。