高放废物缓冲砌块微观结构研究

发布时间：2018-04-30 17:51

本文选题：高放废物处置 + 压实膨润土　；参考：《兰州大学》2017年硕士论文

【摘要】：截止目前,高庙子膨润土与石英砂的混合物已经被确定为我国理想的缓冲回填材料,并展开了大量的可行性研究。室内小试样形状规则、尺寸较小,加工制备条件能够得到理想的控制。但是,在实际的工程处置中,压实砌块必须采用工业化压实设备,批量加工成特定的形状,需要通过工业化放大试验解决关键制备技术以及尺寸效应等问题。兰州大学张虎元研究室参考国内外已有的砌块压制相关研究,开发机械化压实设备,并且提出以1/6和1/12型扇形砌块共同组合的双层缓冲屏障概念模型,确定了扇形缓冲回填材料砌块基本尺寸。本研究分别以黄土砌块和膨润土-砂缓冲砌块为研究对象,通过CT扫描、电镜试验、压汞试验等,分析工业砌块材料的微观结构特征,以期从微观的角度揭示砌块不均匀性的内在原因。主要包括两方面内容:黄土砌块预备试验以及膨润土-砂混合型缓冲砌块微观结构研究。第一部分为黄土砌块预备试验,以萃英山黄土为主要材料,制备目标干密度ρd=1.80 g/cm3,目标含水率ω=13%的1/12型扇形砌块进行CT扫描,通过断层扫描图像观察砌块内部微观结构特征以及定量分析CT图片,从而得到砌块内部沿着不同方向的密度分布。最终证明:黄土砌块内部密度分布沿着不同的方向呈现出规律性分布,其中以高度方向密度变化较为明显。第二部分为膨润土-砂混合型缓冲材料砌块微观结构研究,以1/12型扇形砌块为主要研究对象,设计掺砂率为Rs=30%,目标含水率和目标干密度各不相同的两组平行试验,将制备好的砌块以4×4×4进行分割,并且依据CT试验的结果,选取每个砌块沿着高度方向具有代表性的四个小试块进行电镜扫描和压汞试验,主要结论如下:(1)通过CT断层扫描图片,可以看到,砌块内部存在明显的团聚体。对于同一个砌块,沿着不同的方向,密度呈现出规律性分布。其中沿着高度方向,以中间层为对称点,砌块的密度基本呈对称分布,上下层较大,中间层最小。沿着角度方向,密度分布较为均匀。沿着半径方向,圆中心一侧密度略大于圆周边一侧。(2)通过对比分析压汞试验得到的孔径分布曲线发现:随着干密度的增大,试样内部孔径范围逐渐缩小。随着含水率的增加,试样内部的孔径范围极速扩大。(3)对于同一个砌块,沿着高度方向,孔径分布曲线并没有表现出明显的分布规律。对于含水率相同干密度不同的三个砌块,随着干密度的增大,砌块内部的孔径范围缩小,孔隙结构类型减少,这说明,干密度越大,砌块内部的孔隙大小越均匀。对于干密度相同含水率不同的三个砌块,随着含水率的增加,同一砌块内部孔径范围逐渐扩大,并且孔隙结构类型增加,这说明,含水率越大砌块内部孔隙大小越不均匀。
[Abstract]:Up to now, the mixture of bentonite and quartz has been identified as an ideal cushion backfilling material in China, and a large number of feasibility studies have been carried out. The shape rules of the small specimen, small size, and the preparation conditions can be ideally controlled. However, in the actual engineering treatment, the compaction block must be industrialized. Compacting equipment, which is processed into a specific shape in batch, needs to solve the key preparation technology and size effect through industrial enlargement test. The Zhang Huyuan research room of Lanzhou University, referring to the related research on block pressing existing at home and abroad, develops mechanized compaction equipment, and proposes a double layer of 1/6 and 1/12 type fan-shaped blocks. The concept model of buffer barrier is used to determine the basic size of the fan-shaped cushion backfilling material block. The study is based on the Loess block and bentonite sand buffer block respectively. The microstructure characteristics of the industrial block material are analyzed by CT scanning, electron microscope test and mercury pressure test. The main contents are two aspects: the preparation test of the Loess block and the microstructure study of the bentonite sand mixed type buffer block. The first part is the preparation test of the Loess block. It takes the Yingshan loess as the main material to prepare the target dry density p d=1.80 g/cm3, the target water content omega = 13% 1/12 type sector block for CT scanning, through the fault. The microstructure features of the block and the quantitative analysis of CT images are observed by scanning images, and the density distribution inside the block in different directions is obtained. Finally, it is proved that the distribution of the density distribution in the Loess block is regular in different directions, and the change of the high direction density is more obvious. The second part is bentonite sand mixing. In the study of the microstructure of the combined type buffer material block, the 1/12 type fan block is the main research object. Two groups of parallel tests are designed for the sand mixing rate of Rs=30%, the target water content and the target dry density are different. The prepared blocks are divided by 4 x 4 x 4. According to the results of the CT test, each block is selected along the height direction. The main conclusions are as follows: (1) the main conclusions are as follows: (1) there are obvious aggregates inside the block by CT tomography. For the same block, the density is regularly distributed along different directions. The density of the middle layer is symmetrical and the density of the block along the height direction. It is basically symmetrical distribution, the upper and lower layers are larger, the middle layer is the smallest. Along the angle direction, the density distribution is more uniform. Along the radius direction, the density of the circular center is slightly larger than the round side. (2) through the comparison and analysis of the pore size distribution curve obtained by the pressure mercury test, it is found that the inner aperture range of the sample decreases with the increase of the dry density. (3) for the same block, the pore size distribution curve does not show obvious distribution law for the same block. For the three blocks with the same dry density of the same moisture content, with the increase of dry density, the inner diameter of the block is reduced and the type of pore structure is reduced. This shows that the larger the dry density, the more uniform the size of the pores inside the block. For three blocks with the same dry density, the inner pore size of the same block increases with the increase of water content, and the type of pore structure increases. This shows that the larger the water content is, the more uneven the inner pore size of the block.

【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU522.3

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