实时高温及加卸载作用下非饱和压实膨润土气渗与变形特性研究  

Influences of real-time temperature and stress cycle on gas permeability and deformation characteristics of unsaturated compacted bentonite

作　　者：魏天宇[1,2] 胡大伟 周辉[1,2] 王旭宏 杨球玉[3] 吕涛 侯伟 WEI Tianyu;HU Dawei;ZHOU Hui;WANG Xuhong;YANG Qiuyu;LYU Tao;HOU Wei(State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China;University of Chinese Academy of Sciences,Beijing 100049,China;China Nuclear Power Engineering Co.,Ltd.,Beijing 100840,China)

机构地区：[1]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071 [2]中国科学院大学,北京100049 [3]中国核电工程有限公司,北京100840

出　　处：《岩石力学与工程学报》2022年第3期587-595,共9页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(52179114);中国地质调查局地质调查项目(DD20190128);中国科学院科技服务网络计划(STS计划)项目(KFJ-STS-QYZD-174)。

摘　　要：地下高放废物处置库多场耦合作用复杂,非饱和压实膨润土作为缓冲材料首选材料,需能够有效地将金属罐体表面产生的气体排出到外界以避免气压聚集。采用等效稳态法和应变片,测量样品在不同实时温度及围压加卸载作用下的体积变形和有效气体渗透率,分析变温及围压荷载对样品气渗与变形特性的影响。发现实时高温下,温度升高会增大样品加载时的压缩变形,而对卸载时的变形恢复影响不明显,且相同温度条件下加卸载过程中的有效气体渗透率与样品连通孔隙率之间均存在良好的指数关系。结合NMR扫描结果对升温降低样品气体渗透率的机制做出了解释:(1)升温增大了样品的压缩变形,降低了连通孔隙率;(2)升温加剧了气体分子的滑脱效应,增大了气流通过孔隙通道的阻力;(3)孔隙水受热膨胀改变了其在样品中的分布,进一步压缩了连通孔隙的有效喉径。该试验结果和结论加深了对缓冲材料多物理场耦合作用机制的认识,为工程设计和数值模拟提供了数据支持。The multi-field coupling effect of underground high-level waste repository is complicated. As the first choice of buffer materials,unsaturated compacted bentonite needs to be able to effectively discharge the gas generated on the surface of the metal tank to the outside to avoid pressure accumulation. The quasi-stationary flow method and strain gauges are employed in this paper to measure the volume deformation and the effective gas permeability of two sets of unsaturated compacted bentonite samples under real-time temperature and confining pressure cycle. The influences of real-time temperature and stress cycle on the gas permeability and deformation characteristics of the samples are analyzed. Results suggest that the temperature increment will increase the compression deformation of the samples during loading,but has little effect on the deformation recovery during unloading. And there is a good exponential relationship between the effective gas permeability and the connected porosity of the samples during entire stress cycle under the same temperature condition. Combined with the NMR scan results,the mechanism of decline in gas permeability caused by temperature increasing is explained as:(1)the temperature rise increases the compression deformation of the samples and reduces the connected porosity,(2)the increase in temperature enhances the slippage effect of gas molecules and increases the resistance of air flow through pore channels,and(3) thermal expansion of pore water changes its distribution in the samples and further compresses the effective throat diameter of the connected pores. The present work deepens the understanding of the multi-physics coupling mechanism of buffer materials and provides data support for engineering design and numerical simulation.

关 键 词：土力学 高放废物处置库 缓冲材料 实时温度 气体渗透 

分 类 号：TU43[建筑科学—岩土工程]