| 李辉,谈云志*,彭帆,明华军,刘云.Nano-SiO2和Nano-CaO协同调控膨润土胀-缩行为研究[J].实验力学,2018,33(6):919~928 |
| Nano-SiO2和Nano-CaO协同调控膨润土胀-缩行为研究 |
| Study of the coordinated regulation of bentonite swelling-shrinkage behaviour by Nano-SiO2 and Nano-CaO |
| 投稿时间：2017-08-19 修订日期：2017-11-03 |
| DOI：10.7520/1001-4888-17-171 |
| 中文关键词: 膨润土 膨胀 收缩 纳米氧化钙 纳米氧化硅 |
| 英文关键词:bentonite swelling shrinkage nano-calcium nano-silica |
| 基金项目:国家自然科学基金项目(51579137)；中央财政支持地方高校发展专项项目(8008105) |
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| 中文摘要: |
| 膨润土是用于回填核废料存储库中缓冲层的首选材料。其中，膨胀性是其主要的评价参数之一。膨润土膨胀性太弱，可能导致密实性不够而引起防渗失效；膨胀性太强，则又可能对周边围岩和金属罐产生挤压损伤。选择纳米氧化硅(Nano-SiO2)和纳米氧化钙(Nano-CaO)作为添加剂调控膨润土的胀缩性，发现限制膨胀条件下，添加4%纳米氧化钙和6%纳米氧化硅后，回弹变形率保持在18.2%，但收缩量由21.0%下降到7.2%，说明纳米氧化物既可调控膨润土的膨胀潜势，还可大幅抑制其失水收缩。通过压汞和核磁共振方法，获得不同状态下膨润土混合物试样的孔隙分布特征，发现纳米氧化硅充填了大孔隙，且吸水膨胀后小孔隙因膨润土的“自愈”能力而闭合，从而保证纳米氧化物联合调控下的孔隙度维持在45.4%(纯膨润土为43.6%)；同时，通过扫描电镜试验，获得了纳米氧化物与黏土水化后的微观形貌，发现黏土矿物团(颗)粒间生成了针状的胶结质。以此为基础，构建有(无)约束作用下，压实膨润土混合物的胀缩过程概念模型，阐述了纳米氧化硅和纳米氧化钙联合调控膨润土胀缩性的机制。 |
| 英文摘要: |
| Bentonite is the preferred material for backfilling of buffer layer in nuclear waste repository. Among them, swelling property is one of its main evaluation parameters. If the swelling property of bentonite is too weak, it may lead to impermeability failure due to insufficient compactness; if swelling property is too strong, it may cause extrusion damage to surrounding rock and metal tank. Selecting Nano-silica and Nano-calcium oxide as additives to control the swelling and shrinkage of bentonite, under the condition of limited expansion, it is found that after adding 4% Nano-calcium oxide and 6% Nano-silica, the rebound deformation rate is remained at 18.2%, but the shrinkage decreases from 21.0% to 7.2%. Experimental results show that Nano-oxide can not only regulate the swelling potential of bentonite, but also significantly inhibit the shrinkage due to water loss. The pore distribution characteristics of bentonite mixture samples in different states were obtained by using mercury injection porosimeter (MIP) and nuclear magnetic resonance (NMR). It is found that Nano-silica has filled large pores, and the small pores are closed due to the self-healing ability of the bentonite after water absorption and swelling. Thus it ensures that the porosity under the combined control of nano-oxide is maintained at 45.4% (43.6% for pure bentonite). Meanwhile, the micro-morphology of nano-oxide and clay hydration is obtained by scanning electron microscope (SEM). Needle-shaped cements are found between clay particles. Concept models of compacted bentonite mixture are built for swelling-shrinkage process under different restricted conditions, which describes the swelling and shrinkage adjusted mechanism for bentonite by adding Nano-silica and Nano-calcia. |
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