缓冲回填材料砌块接缝密封及愈合研究  

Sealing and healing of compacted bentonite block joints in HLW disposal

作　　者：张虎元[1,2] 王学文[2] 刘平[1,2] 闫铭[2] 彭宇[2] 

机构地区：[1]兰州大学西部灾害与环境力学教育部重点实验室,甘肃兰州730000 [2]兰州大学土木工程与力学学院,甘肃兰州730000

出　　处：《岩石力学与工程学报》2016年第A02期3605-3614,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家国防科技工业局研究项目"缓冲回填材料砌块关键制备技术及其工程性质研究";国家自然科学基金资助项目(41672261);兰州大学中央高校基本科研业务费专项(lzujbky–2016–k15)~~

摘　　要：高放废物地质处置多重屏障体系中,缓冲回填材料砌块接缝构成潜在的＂水力缺陷＂和强度薄弱部位。室内试验制备压实膨润土模拟接缝试样,设置接缝宽度为2 mm,采用膨润土干粉、膨润土泥浆、微粒膨润土3种材料对接缝进行密封。将含接缝试样进行柔性壁渗透试验,之后开展热传导试验,评价砌缝不同密封形式愈合效果的差别。自然堆填密度和自由膨胀率试验得到,颗粒粒组为0.25-0.5 mm,且颗粒率为70%时,微粒膨润土达到最佳组构。试验数据表明,不同密封处理的含接缝试样的水力传导系数范围为（2.51-4.94）×10-10 cm/s,其水力传导系数Rg由小到大的顺序为Rg=70%微粒砌缝、Rg=90%微粒砌缝、Rg=50%微粒砌缝、泥浆砌缝、Rg=30%微粒砌缝和干粉砌缝,与接缝密封材料初始填充干密度成负相关。沿着接缝方向,各试样的平均热传导系数范围为1.43-1.63 W/（m·k）,其中Rg=70%微粒膨润土砌缝的导热性能最好。垂直接缝方向,各试样的热传导系数基本呈现出接缝愈合带略小于接缝两侧的趋势。研究证实,膨润土干粉、膨润土泥浆和微粒膨润土3种形式的密封材料中,Rg=70%微粒膨润土是优良的密封材料,密封后的接缝愈合效果最佳。随着试样不断饱水膨胀,接缝带干密度提高,接缝结构面逐渐愈合消失,愈合带水力传导性质和热传导性质与砌块材料逐渐趋于一致。Within the multi-barrier system for high-level waste（HLW） disposal,compacted bentonite blocks joints play as potential ＂hydraulic defects＂ with low strength. Block joint with a width of 2 mm were prepared and back-filled with different materials such as bentonite powder,bentonite sludge in plastic limit,and the mixtures of bentonite pellet-powder with a pellet ratio of 30%,50%,70% and 90%,respectively. This paper tends to evaluate the sealing and healing effects of the joints with different treatments by hydraulic and thermal conductivity tests in laboratory. The bentonite pellet-powder mixture with pellet size in 0.25–0.5 mm and 70% pellet content exhibits highest filling density and therefore possess high swelling potential. Tests data show that the hydraulic conductivity of specimens varies between K =（2.51–4.94）×10-10 cm/s,increasing with the decrease of initial bulk density of bentonite sealing material for joints treated by Rg = 70% pellet-powder,Rg = 90% pellet-powder,Rg = 50% pellet-powder,bentonite sludge in plastic limit,Rg = 30% pellet-powder and bentonite powder. The average thermal conductivities along joints vary between λ = 1.43-1.63 W/（m·k）,among which the highest is the joint treated by Rg = 70% pellet-powder. On the contrary,thermal conductivity along the direction perpendicular to the joint displays a little lower at the joint than the other parts. This study confirms that Rg = 70% bentonite pellet-powder mixture is the best sealing material among the three materials tested. With bentonite hydration and swelling,joints tend to be healed as a result of increase in dry density of sealing materials,and exhibit comparatively uniform hydraulic and thermal conductivity properties as compacted block.

关 键 词：高放废物 接缝密封 微粒膨润土 水力传导系数 

分 类 号：X70[环境科学与工程—环境工程]