Comparative Tests for Evaluating Permeability Changes of a Compacted Bentonite/Sand Mixture During Shear
Comparative Tests for Evaluating Permeability Changes of a Compacted Bentonite/Sand Mixture During Shear
复制标题
评估压实膨润土/砂混合物在剪切过程中渗透率变化的比较试验
DOI：
10.1557/proc-465-979
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Y. Mitani
中科院分区：
文献类型：
--
作者：
T. Esaki;Ming Zhang;Y. Mitani
一种致密的库尼格鲁六号膨润土和D-砂混合物正被考虑用作日本低放射性废物处置设施的工程屏障。一个重要的问题是在剪切过程中保持混合物的延迟特性，这可能是由于地震和/或在设施设计寿命期间发生的逐渐构造变形引起的。为了研究这一问题，利用最新研制的剪切渗透率耦合测试仪，在温控条件下对膨润土-砂混合物和高岭土-砂混合物进行了对比试验。除了渗透率外，还利用恒流渗透率试验的新解析理论对膨润土-砂样在剪切过程中的比储存量进行了系统的评价。研究表明：1)恒流泵法测定极低渗透材料的渗透率宜采用温控法；2)在3%以下的剪切应变对库尼格鲁VI膨润土与D-砂(膨润土与砂的重量比为15：85)混合物的渗透率和比储存量影响不大，而高岭土-砂混合物的渗透率随剪应变的增加而几乎呈线性增加；3)膨润土在低围应力下的膨胀降低了膨润土-砂混合物的渗透率和比储存量。膨润土的这一特性有助于保持混合物的长期缓凝性能；4)恒流渗透性试验方法与新的理论分析相结合，有望成为快速和系统地研究水力坡度相对较低(即接近现场)的极低渗透材料的渗透率和特定储存量的非常有效的手段。这对于工程护栏的设计和长期性能评估是必要的。
A compacted mixture of Kunigeru VI bentonite and D-sand is being considered for use as an engineered barrier in low-level radioactive waste disposal facilities in Japan. An important issue is the maintenance of the retardation property of the mixture during shear that might be induced in such barriers by earthquakes and/or gradual tectonic deformations occurring over the design life of the facility. To investigate this issue, comparative tests on a bentonite-sand mixture and kaolin-sand mixture were conducted by means of a recently-developed coupled shear and permeability testing apparatus under temperature controlled condition. In addition to permeability, the specific storage of bentonite-sand specimen during shear is also systematically evaluated with the new analytical theory for the constant flow permeability test. The present study reveals that 1) temperature control is preferred for measuring the permeability of extremely-low permeability materials with the constant-flow pump method; 2) both the permeability and specific storage of the mixture of Kunigeru VI bentonite and D-sand (bentonite to sand weight ratio = 15: 85) were not significantly influenced by shear strains up to 3% whereas the permeability of the kaolin-sand mixture increased almost linearly with the increment of shear strain; 3) the swelling of bentonite in the mixture under low confining stress decreases both the permeability and specific storage of bentonite-sand mixture. This feature of bentonite helps maintain the long-term retardation property of the mixture; and 4) the constant flow permeability test method, with the newly derived theoretical analysis, promises to become a very effective means of investigating, rapidly and systematically, the permeability and specific storage of extremely-low permeability materials with relatively-low (i.e. close to in situ) hydraulic gradients. This is necessary for the design and long-term performance assessment of engineered barriers.