混合型缓冲回填材料砌块接缝渗透特性研究

发布时间：2018-03-06 05:35

本文选题：地下放大试验　切入点：砌块接缝　出处：《兰州大学》2015年硕士论文　论文类型：学位论文

【摘要】：目前,世界部分国家已从室内试验转移至地下放大试验研究。一般认为,堆砌法比较适用于处置罐体所在的污染缓冲区。采用堆砌法将缓冲回填砌块材料进行拼接,会产生砌块接缝。砌块接缝作为缓冲回填材料的“水力缺陷”,其防渗性能成为地质处置工程中的薄弱部位,其接缝处的膨胀自愈能力及防渗性能已成为首要关注的核心问题。本文选用高庙子膨润土和石英砂作为缓冲回填材料,用静立压实法将混合物制成干密度1.7g/cm3和掺砂量30%的完整圆饼状和圆饼中间分割状试样。设置砌缝宽度为2mm,并用膨润土粉末、塑限状态膨润土以及粒径为0.25-0.5mm且干密度为1.8g/cm3的膨润土颗粒与膨润土粉末按30%,50%,70%和90%不同比例混合分别作为不同接缝处的材料,以完整试样作为对比参照,利用柔性壁渗透仪对不同接缝处理形式的压实砌块进行渗透试验,并测量试样愈合后的导热性能及微观结构的变化,研究不同接缝处理形式的膨胀自愈能力和防渗性能。研究表明：以完整试样作对比,各接缝处理形式的水力传导系数的范围为(2.51-4.94)×10-10 cm/s,其中颗粒率为70%的接缝形式的渗透性较低,且其愈合后接缝处微观结构的颗粒排列较为紧密,孔隙较小且分布密集,愈合程度较好；各接缝处理形式接缝处的平均热传导系数范围为1.43-1.63W/(m·k),其中颗粒率为70%的砌缝的平均热传导系数为最大,其导热性能较好。除干粉和膏状的其他接缝形式沿着接缝方向的热传导系数的方差相差不大,且方差数值较小,认为这几种接缝处理形式的导热性能较为稳定。结合以上试验研究,选取颗粒率为70%的砌缝为最佳接缝处理形式。砌块接缝愈合机理研究表明,一方面,膨润土材料遇水膨胀后,会形成一层薄膜包裹在石英砂颗粒表面,并逐渐填充石英砂颗粒之间的孔隙；另一方面接缝处的膨润土材料与膨润土砌块共同遇水膨胀,在此作用下,膨润土颗粒之间的大孔隙逐渐被填充形成许多小孔隙,并在较大的围压作用下,接缝与膨润土砌块之间结构进行重组,原有的接缝结构面逐渐消失,接缝处的密度与接缝附近的密度逐渐趋于一致,即接缝愈合。
[Abstract]:At present, some countries in the world have transferred from indoor test to underground amplification test. It is generally considered that the stacking method is more suitable for disposal of the polluted buffer zone where the tank body is located, and the cushioning backfill block material is jointed by the stacking method. Block joints will be produced. Block joints are "hydraulic defects" of cushioning backfill materials, and their impermeability becomes a weak part in geological disposal projects. The expansion self-healing capacity and impermeability of the joints have become the core issues of primary concern. In this paper, the high temple bentonite and quartz sand are used as buffer backfill materials. The mixture was prepared by static compaction method into complete round cake and round cake with dry density of 1.7 g / cm ~ 3 and sand content of 30%. The width of joint was set at 2 mm and bentonite powder was used. The plastic-limited bentonite and bentonite particles with a dry density of 1.8 g / cm ~ 3 with a diameter of 0.25-0.5 mm and a dry density of 1.8 g / cm ~ 3 were mixed with bentonite powder at different proportions of 30% and 50% and 90% respectively as materials for different joints. The permeation tests of compacted blocks with different joint types were carried out by using a flexible wall permeation apparatus, and the thermal conductivity and microstructure of the specimens after healing were measured. The expansion self-healing ability and impermeability of different joint treatment forms are studied. The results show that the hydraulic conductivity coefficient of each joint treatment form is in the range of 2.51-4.94) 脳 10 ~ (-10) cm / s, and the permeability of the joint form with particle ratio of 70% is lower than that of the whole joint treatment, and the hydraulic conductivity coefficient of each joint treatment form is in the range of 2.51-4.94 脳 10 ~ (-10) cm / s. The microstructure of the joint after healing is closely arranged, the porosity is small and the distribution is dense, and the degree of healing is better. The average heat conduction coefficient of each joint is 1.43-1.63W / m 路kg, and the average thermal conductivity of the joint with particle ratio of 70% is the largest. Its thermal conductivity is better. Except for dry powder and other joint forms, the variance of thermal conductivity along the joint direction is not different, and the variance value is small. It is considered that the thermal conductivity of these joint treatment forms is relatively stable. In combination with the above experimental study, the best joint treatment form is selected with particle ratio of 70%. The research on the mechanism of block joint healing shows that, on the one hand, When the bentonite material is swelled by water, it will form a film wrapped on the surface of quartz sand grain and gradually fill the pores between quartz sand particles. On the other hand, the bentonite material at the joint and the bentonite block will meet water expansion together, and under this action, The macropores between bentonite particles are gradually filled into many small pores, and under the action of larger confining pressure, the structure between the joint and the bentonite block is reorganized, and the original joint structure surface gradually disappears. The density of the joint tends to be consistent with the density near the joint, that is, joint healing.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU522.3

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