| 石墨?膨润土缓冲材料的最优配置方法 |
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| 引用本文： | 谈云志,彭帆,钱芳红,孙德安,明华军.石墨?膨润土缓冲材料的最优配置方法[J].岩土力学,2019,40(9):3387-3396. |
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| 作者姓名： | 谈云志 彭帆 钱芳红 孙德安 明华军 |
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| 作者单位： | 1. 三峡大学 三峡库区地质灾害教育部重点实验室，湖北 宜昌 443002；2. 三峡大学 特殊土资源化利用宜昌市重点实验室，湖北 宜昌 443002；3. 上海大学 土木工程系，上海 200444；4. 三峡大学 湖北省水电工程施工与管理重点实验室，湖北 宜昌 443002 |
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| 基金项目： | 三峡库区地质灾害与教育部重点实验室开放基金（No.2018KDZ05）；国家自然科学基金项目（No.51579137，No.51609126）；湖北省优秀中青年科技创新团队计划项目（No.T201803）；三峡大学学位论文培优基金项目资助（2019SSPY022）。 |
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| 摘 要： | 核废料封存到处置库后还会继续释放衰变热，需要加快热量向周边围岩消散，确保处置库处于安全运行状态。而提高缓冲层的导热性能成为解决该问题的突破口。将天然石墨粉掺入到钠基膨润土中，以期配置成导热速度快、隔离能力强的缓冲层回填材料。通过开展石墨?膨润土混合物的自由膨胀率、恒体积膨胀力、饱和渗透系数和导热系数等试验，研究石墨掺入率（Rg分别为5%、10%、15%、20%、30%、40%）和不同粒径（297、150、74、44 μm）对其水?力?热性能的影响规律。结果表明，掺入石墨后显著提高了膨润土的导热性能，但其提升幅度受石墨掺入率、初始含水率和初始干密度等因素影响。综合分析石墨?膨润土混合物的水?力?热性能参数，发现最优石墨掺入率处于15%～20%（质量比）范围内；相同石墨掺入率下石墨粒径为150 μm或74 μm时混合物的水?力性能最优。石墨?膨润土混合物压实后的孔隙分布显示，相同石墨掺入率下石墨粒径过大或者过小都易形成大孔隙。究其原因，天然鳞片状石墨呈扁平状，大部分膨润土颗（团）粒小于石墨，与石墨属于点?面接触方式。尤其是压实程度不高时，膨润土颗（团）粒和石墨接触面处存在大量的孔隙；而且石墨属于憎水性材料，对水分子的拖拽力弱，即使膨润土吸水膨胀后，水分也容易从石墨薄片表面处通过。
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| 关 键 词： | 石墨?膨润土 粒度 导热系数 孔隙分布 |
| 收稿时间： | 2018-06-19 |
Optimal mixed scheme of graphite-bentonite buffer material |
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| TAN Yun-zhi,PENG Fan,QIAN Fang-hong,SUN De-an,MING Hua-jun.Optimal mixed scheme of graphite-bentonite buffer material[J].Rock and Soil Mechanics,2019,40(9):3387-3396. |
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| Authors: | TAN Yun-zhi PENG Fan QIAN Fang-hong SUN De-an MING Hua-jun |
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| Abstract: | Nuclear waste continuously releases the decay heat after it being stored in the disposal repository. For the safe operation of the disposal repository, it is necessary to accelerate the decay heat to dissipate to surrounding rock. A good solution to solve this problem is to improve the thermal conductivity performance of buffer layers. In this study, the natural graphite powder was mixed into Na-bentonite as backfilling material, which can exert both of their advantages: fast heat conduction for graphite and isolated function of buffer materials. A series of tests, including swelling pressure, free swelling ratio, permeability and thermal conductivity, was conducted on the graphite-bentonite mixture with different graphite contents (Rg = 5%, 10%, 15%, 20%, 30%, 40%) and different granularities (297, 150, 74, 44 μm). The hydro-mechanical-thermal performance of mixtures showed that the added graphite improved the thermal conductivity significantly, and its influence degree depended on the graphite content, initial water content and dry density. Based on parameters of hydro-mechanical-thermal performance, it was found that the optimum graphite content was about 15%?20% (Wt.), and the graphite with a particle size of 150 μm or 74 μm was more beneficial for the optimum requirements. The pore-size distribution curves of the compacted mixture showed that too large or too small graphite particles were conducive to form macropores easily with the same graphite content. The reason is that as the natural graphite particles are flat and a majority of bentonite particles or agglomerates are smaller than graphite, they are formed in the point-edge contacted mode. Especially for
mixtures compacted relatively loose, there are a large number of pores at the contact interface between bentonite and graphite. Moreover, graphite is hydrophobic with a low capacity for adsorbing water molecules. Hence, water can easily pass through the surface of the graphite sheet, even after the bentonite is swollen by soaking sufficiently. |
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| Keywords: | graphite-bentonite particle size thermal conductivity pore size distribution |
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