非饱和水通过双层孔隙介质渗流的定量实验

QUANTITATIVE EXPERIMENT OF UNSATURATED WATER VADOSE THROUGH TWO-LAYER POROUS MEDIA

非饱和水通过双层孔隙介质的渗流对于放射性废物近地表处置库的顶盖设计具有重要意义。本文主要介绍非饱和水通过以黄土 (细颗粒 )和石英砂 (粗颗粒 )组成的双层孔隙介质渗流定量实验的装置、方法及其结果。从实验结果可见 :黄土中的非饱和水在下渗过程中遇到石英砂层时 ,即使石英砂层很薄 ,且粒度很小 ,下渗水也发生绕流现象 ;相对绕流量的大小随水的喷淋强度的增大而减小 ,随石英砂层厚度的增加而增加。另外 ,实验发现 ,相当部分的绕流水是紧贴石英砂层的下表面运动的。由实验结果推断 ,在石英砂粒径 0 .2～ 0 .4 5 mm、埋深 2 0 cm情况下 ,不起绕流作用的石英砂层厚度≤ 1mm;对于≥ 2mm厚的石英砂层 ,相对绕流量达 10 0 %的喷淋强度需低于 5 mm/

It is of very important significance to understand unsaturated water vadose through two layer porous media in design of cover of near surface repository of radioactive waste. The device, method and results of the quantitative experiment of unsaturated water vadose through two layer porous media, made up of loess (fine particle layer) and quartz sand (coarse particle layer), are introduced in this paper. It can be seen from the experiment that the detouring flow phenomenon of infiltration water occurred when the infiltrated unsaturated water from loess encounters quartz sand layer even though the quartz sand layer is very thin. The relative detouring flow amount decreases with increase of sprinkling rate and increases with thickness of quartz sand layer. Moreover, it is found from the experiment that some of detouring flow water moves close to lower surface of the quartz sand layer. From the deduced results by this experiment, it can be seen that the thickness of quartz sand layer, by which detouring flow do not happen, is less than or equal to 1 mm and the sprinkling rate, at which relative detouring flow amount is up to 100%, is less than 5 mm/d when thickness of the quartz sand layer is greater than or equal to 2 mm. (