盐溶液对高庙子钠基膨润土膨胀性能的影响

The Influence of the Salt Solution on Swelling Property of Gaomiaozi Na-bentonite

内蒙古高庙子钠基膨润土被确定为我国高放核废物深地质处置库的缓冲回填材料,为研究其在化学屏障方面的表现,对在NaCl,KCl,CaCl_2,MgCl_24种浓度均为0.5 mol/L的盐溶液及蒸馏水入渗下的内蒙古高庙子钠基膨润土试样进行了自由膨胀率及膨胀力试验。结果表明:膨润土试样的竖向膨胀力大于其径向膨胀力,且在初始阶段膨润土膨胀力发展迅速,一段时间后增长减缓并趋于稳定;盐溶液作用下的膨润土膨胀性能发生了衰减,且不同盐溶液(即不同金属阳离子)对膨润土膨胀性能有着显著不同的影响;膨润土的自由膨胀率与其膨胀力成正相关,即自由膨胀率越大,则相应的膨胀力也越大,Na^+,K^+对高庙子钠基膨润土膨胀性能的削弱作用均要强于Ca^(2+),Mg^(2+),即在研究范围内,低价阳离子对高庙子钠基膨润土膨胀性能的影响要大于高价阳离子;膨润土径向膨胀力与竖向膨胀力的比值为0.6左右,且该比值与入渗液的种类无关。研究结果可为高庙子钠基膨润土化学屏障性能的判定提供依据。

Gaomiaozi Na-bentonite has been identified as the buffer/backfilling materials as barriers in high level radioactive waste disposal system in our country. In order to study its performance in chemical barrier,the free expansion ratio and expansion force tests of Gaomiaozi Na-bentonite under the salt solu-tion of NaCl,KCl,CaCl2 ,MgCl2 with a concentration of 0. 5 mol/L were carried out. The results show that the vertical expansion force of bentonite is greater than its radial expansion force. The swelling force of bentonite develops rapidly in the initial stage and its growth is slow and stable after a period of time. The swelling properties of bentonite under the salt solution have been attenuated and the different salt so-lution（different metal cation）has a significant and different effect on the swelling properties of bentonite. The free swelling ratio of bentonite is positively correlated with its swelling force：The larger its free ex-pansion ratio,the larger its swelling force. The weakening effect of Na＋and K＋ on the expansion perform-ance of Gaomiaozi Na-bentonite is greater than that of Ca2＋and Mg2＋. Within the scope of the study,the influence of low valent cation on the expansion performance of Gaomiaozi Na-bentonite is greater than that of high valent cation. The ratio of radial expansion force and vertical expansion force is about 0. 6,and it has no relevance with the type of leachate. The results of the study have a guiding significance for the judgment of the performance of Gaomiaozi Na-bentonite chemical barrier.