非饱和带中非均质条件下LNAPL运移与分布特性实验研究

本文通过室内实验建立物理模型，研究非饱和带中层状非均质条件下轻非水相液体LNAPL（Light Non-Aqueous Phase Liquid）运移机制和分布特性。实验结果发现，介质的结构突变面改变了LNAPL的迁移模式。在LNAPL到达干湿界面以后，由于毛细水压力的作用，其入渗速度明显加快。当LNAPL迁移到夹层上界面时，纵向迁移受到阻碍。随着入渗过程的继续，污染物沿着界面产生向右横向迁移；在夹层上界面下部出现“优势流”现象，污染物由集中走向分散，随着分散块的体积不断增大，最终污染物又连接到一起，由分散走向集中；在夹层下界面附近锋面线集中在一起，说明污染物向下的纵向迁移基本停止。另外，介质的局部密实“透镜体”对LNAPL的局部迁移起到“阻滞”作用，并迫使其改变迁移路径。地下水位的变动将使污染物的产生重新分布。当地下水位降低以后，污染物产生明显的向下迁移。

An experimental investigation of LNAPL migration and redistribution in unsaturated heterogeneous porous media

In this paper,the migration mechanism and redistribution characteristics of LNAPL in unsaturated layered heterogeneous porous media were examined by building a physical model through a laboratory experiment.A digital camera was used to take pictures during the experiment.The dispersive process of LNAPL was copied in images,and the images were analyzed and processed subsequently.The results of the experiment show that the migration model of LNAPL was changed with the structure face of media mutation.After reaching top of capillary fringe, the velocity of LNAPL increased obviously because of capillary pressure.When LNAPL reached the upper interface of the interlayer its vertical migration was blocked.As infiltration process continued the contamination produced horizontal migration to the right along the interface;"preferential flow" phenomenon was found below the upper interface of the interlayer,and the contamination was separated from the integrity.As the size of the separated block enlarged,the contamination got together sequentially,and came to integrity from separation.The lines of LNAPL edge concentrated near the second interface of the interlayer,which suggested that downwards migration was blocked.In addition,the local dense "lens" of the porous media had "errest" effect on the local migration of LNAPL,which made the contamination change the path of infiltration.Fluctuation in ground water table would make the contamination redistribute.After ground water table got down,LNAPL had an obvious downward migration.