考虑到缓冲材料膨润土块体从制作到浸水的时间很长, 需要分析膨润土膨胀特性的时效性. 以高庙子钠基膨润土为试验材料, 在保持试样干密度和含水率不变条件下, 分别静置 0, 7, 15, 30 和 90 d, 利用单向固结仪进行不同总溶解固体 (total dissolved solid, TDS) 浓度溶液饱和的膨胀力和膨胀变形试验, 同时完成部分试样的扫描电镜 (scanning electron microscope, SEM) 试验. 试验结果表明, 在相同初始状态下, 高庙子膨润土膨胀变形和膨胀力随静置时间增长不断减小, 且前期衰减明显, 后期趋于稳定; 相同静置时间下, TDS 浓度增加, 膨胀特性衰减的时效性减弱. SEM 测试结果表明: 随着静置时间增加, 膨润土发生水化分解, 聚集体间的孔隙趋于均质化; 相比于静置时间增长, TDS 浓度增加引起的聚集体间的孔隙变化更大, 这与膨胀力衰减率得出的结论相吻合, 即在低 TDS 浓度和较短静置时间的条件下, TDS 浓度相比于静置时间对膨胀力的衰减影响可能更为明显.

There is a long time gap between buffer bentonite block preparation and wetting; thus, it is necessary to study the effect of ageing on swelling characteristics. Gaomiaozi (GMZ) sodium bentonite was used as the test material, and curing periods of 0, 7, 15, 30, and 90 days after preparation were chosen, while maintaining constant dry density and water content. The swelling deformation and pressure tests were performed by saturating the specimens with salt solutions in an odometer. Scanning electron microscope (SEM) was also performed. The test results showed that the swelling deformation and pressure of GMZ bentonite decreased with increasing curing time. The decrease was obvious in the early stage, and it tended to be stable in the later stage. At the same curing time, the ageing effect on the swelling property weakened when the TDS concentration increased. The SEM images revealed that upon increasing the ageing time and TDS concentration, the bentonite was hydrolysed and the pores between the aggregates tended to be homogenised. The variance of pores between the aggregates caused by increasing TDS concentration was larger than that caused by increasing ageing time. This is consistent with the conclusion for the swelling force attenuation rate: under the condition of low TDS concentration and short ageing time, the TDS concentration may have a more obvious influence than the ageing time.