包气带中裂隙对轻非水相流体运移和分布影响的模拟研究

Simulation of fracture impacts on light non-aqueous phase liquids migration and distribution in the unsaturated zone

岩土体中存在的大孔隙、裂隙等,使其呈现出强烈的非均质性。相比均质介质和不含裂隙的非均质介质,轻非水相流体(Light Non-aqueous Phase Liquids,LNAPLs)会优先通过裂隙管道进入土壤中,其运移规律更为复杂,造成的污染更为严重。为此,研究LNAPL在含裂隙基质中的运移与分布规律显得很有必要,研究成果将为裂隙发育区域的污染修复提供理论依据。本文通过室内试验和TOUGH2数值模型分析了裂隙对LNAPL运移及分布的影响。经过分析发现,LNAPL注入后,裂隙中的压强迅速增加,形成以裂隙为核心的、压强逐渐减小的辐射区;LNAPL优先流入裂隙中,以裂隙为核心向四周缓慢扩散,形成圈层状的饱和度逐渐减小的分布区;相同条件下,裂隙越长,同时刻LNAPL的污染面积越大,LNAPL到达饱水带的时间也越短;裂隙的存在,起到了"快速通道"的作用,使得LNAPL在短时间内渗入土壤中,造成严重的污染。

Macropore and fracture make rock-soil mass present strong anisotropy. Compared with the homo-geneous medium and heterogeneous medium without fracture, Light Non-aqueous Phase Liquids（LNAPL）priority through fracture into the soil,its migration law is more complex,and cause more serious pollution.Therefore, the study on migration and distribution of LNAPL in soil with fracture is very necessary, andthe results will provide a theoretical basis for the remediation of zone with fracture. In this paper, the ef-fect of fracture on LNAPL migration and distribution was examined through laboratory investigation andTOUGH2 numerical simulation. The results indicate that the pressure in fracture increased rapidly andformed a radiative zone that the fracture as the core,the pressure decreased slowly;LNAPL infiltrates intofracture first, and formed a fracture-centered zone that the LNAPL saturation decreased slowly. The longerthe fracture is,the bigger the contaminated area of LNAPL will be,and the shorter the time that LNAPLwould take to reach the aquifer under a same situation. The fractures have an effect of ＂fast track＂,whichwould make the LNAPL infiltrates the soil in a short time,and cause a serious pollution.