Microstructure of saturated bentonites characterized by X-ray CT observations
Microstructure of saturated bentonites characterized by X-ray CT observations
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DOI：
10.1016/j.enggeo.2009.02.013
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发表时间：
2009-05-28
影响因子：
7.4
通讯作者：
Kaneko, Katsuhiko
中科院分区：
文献类型：
--
作者：
Kawaragi, Chie;Yoneda, Tetsuro;Kaneko, Katsuhiko
膨润土是一种非常有吸引力的原材料，可用作一般废物处置场的压实粘土衬垫，也可用作放射性废物处置场的缓冲材料。膨润土的渗透性是评价防渗材料最重要的指标，它与其微观结构密切相关。最近在地质材料科学中的研究表明，X射线计算机断层扫描（X射线CT）对于微观结构和水渗透现象的研究是非常强大的（例如Wong和Wibowo [Wong，R.，Wibowo河，2000.土柱中空气和水流动模式的层析成像评价。地质技术Test. J. 23，413-422]）。通过对怀俄明州膨润土的渗透性试验和显微X射线CT观察，研究了膨润土作为防渗材料时的微观结构与渗透性之间的关系。采用压实的膨润土-石英砂混合物和膨润土原矿两种样品，对膨润土-石英砂混合物进行了X射线CT观察，结果表明，膨润土样品经水渗透后，在X射线CT图像上可区分出“空孔”和“膨润土-水复合体”，其微观结构的差异与样品的渗透性密切相关，并且取决于混合和饱和条件。膨润土矿样的渗透性试验和X射线CT观察表明，渗透性和微观结构与矿样内部发育的沉积结构无关。此外，具有微裂纹的膨润土矿样具有较低的导水率，与压实的膨润土粉末相当，这意味着样品中的裂纹被渗透后形成的“膨润土-水复合物”所填充。皇冠版权所有（C）2009年出版的爱思唯尔B. V.保留所有权利。
Bentonite is a very attractive raw material as a compacted clay liner at general waste disposal sites and also as a buffer material at radioactive waste disposal sites. It has been considered that the permeability of bentonite, the most important index for evaluating barrier materials, is closely related to its microstructure. Recent studies in geological material science show that X-ray computerized tomography (X-ray CT) is a very powerful too[ for the study on microstructure and hydro-osmotic phenomena (e.g. Wong and Wibowo [Wong, R., Wibowo, R., 2000. Tomographic evaluation of air and water flow patterns in soil column. Geotech. Test. J. 23, 413-422]). Permeability tests and micro X-ray CT observations of Wyoming bentonite were performed to describe the relationship between microstructure and permeability of the bentonite used as a barrier material. Two types of samples, compacted bentonite-quartz sand mixtures and raw bentonite ores, were used in this study.The X-ray CT observations of the bentonite-quartz sand mixtures show that 'vacant pores' and 'bentonite-water complexes' of the bentonite samples after water permeation are distinguishable in X-ray CT images, and that the micro-structural differences are closely relating to the sample permeability, and depend on the mixing and saturation conditions. Permeability tests and X-ray CT observations of the bentonite ore samples show that the permeability and the microstructure are independent to the sedimentary texture developed within the ore samples. In addition, it is characteristic that the bentonite ore samples with micro-cracks show low hydraulic conductivity, comparable to the compacted powder bentonite, implying that cracks in the sample are filled with 'bentonite-water complexes' formed after permeation. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.