The three-dimensional swelling pressure tests on the compacted Gaomiaozi (GMZ) bentonite–sand mixtures are carried out under different dry densities, sand contents and temperatures. The results show that anisotropy of swelling pressure is observed in the mixtures and the vertical swelling pressure is greater than the horizontal swelling pressure in the range of test conditions (dry densities of 1.6, 1.7, 1.8 and 1.9 g/cm³, sand contents of 0, 10%, 20% and 30%, temperatures of 30, 45, 60 and 75 ℃). The development of swelling pressure with time shows significant stage characteristics. The three-dimensional swelling pressure increases rapidly before 400 min, basically reaching 85% of the ultimate swelling pressure, and reaches equilibrium within 1400 min. The ratio of horizontal swelling pressure to vertical swelling pressure decreases with increasing dry density, which is about 0.87 when the dry density is greater than 1.8 g/cm³. When the sand content is above 20%, the increase of sand content has little effect on anisotropy. When the sand contents are the same, the vertical swelling pressure of the bentonite–sand mixtures increases with the enlargement of the dry density at temperature of 30 ℃. Under the same temperatures and dry densities, the three-dimensional swelling pressure decreases linearly with the increase of the sand content. Moreover, the slope of the relation curve increases linearly with the dry density. In the range of dry densities, when the temperature is higher than 45 ℃, the vertical swelling pressure decreases with the increase of temperature. The experimental results are of reference value for design of buffer/backfill materials in high-level radioactive waste (HLW) repository.

在不同干密度、砂含量和温度下对压实的高庙子（GMZ）膨润土-砂混合物进行三维膨胀压力试验。结果表明，在试验条件范围内（干密度为1.6、1.7、1.8和1.9 g/cm ^{3 ）}，混合物中的溶胀压力具有各向异性，垂直溶胀压力大于水平溶胀压力。，含砂量0、10%、20%和30%，温度30、45、60和75℃）。膨胀压力随时间的发展表现出显着的阶段性特征。三维溶胀压力在400 min前迅速升高，基本达到极限溶胀压力的85%，并在1400 min内达到平衡。水平膨胀压力与垂直膨胀压力之比随着干密度的增加而减小，当干密度大于1.8 g/cm ³时约为0.87. 当含砂量在20%以上时，含砂量的增加对各向异性影响不大。当砂含量相同时，膨润土-砂混合物的垂直膨胀压力随着温度30℃干密度的增大而增大。在相同的温度和干密度下，三维膨胀压力随着含砂量的增加而线性降低。此外，关系曲线的斜率随干密度线性增加。在干密度范围内，当温度高于45℃时，垂直膨胀压力随着温度的升高而降低。实验结果对高放废物处置库缓冲/回填材料的设计具有参考价值。