黏滞性对LNAPL 在非饱和多孔介质中优先流影响的试验研究

为探究轻非水相液体(LNAPL)在非饱和带通过裂隙快速通道产生的优先流对地下含水层造成污染的影响,选取大豆油和0号柴油2种不同黏滞性的LNAPL,通过室内试验,研究不同黏滞性的LNAPL在通过非饱和多孔介质中单裂隙快速通道产生的优先流迁移规律。试验结果表明:黏滞性小的LNAPL通过裂隙产生的优先流的运移速度快;LNAPL进入地下水毛细带后受毛细水的顶托力作用,垂向迁移速率减缓,横向扩散速度增大,LNAPL优先流锋面形态逐渐变缓;优先流不仅能通过裂隙非均质条件产生,而且可以在基质中以指流的形式存在,黏滞性大的LNAPL更容易产生多个狭长形的指流。

Experimental study of impacts of viscosity of LNAPL on preferential flow in unsaturated porous media

In order to study the influence of the preferential flow formed in the facture by light non-aqueous phase liquids (LNAPLs) in the unsaturated zone on contamination of the aquifer, we experimentally investigated the migration behavior of the preferential flow formed in a single fracture by LNAPLs with different viscosities in the unsaturated porous media, selecting soybean oil and No. 0 diesel fuel as two LNAPLs with different viscosities. The results indicate that the LNAPL with lower viscosity forms a faster preferential flow in the fracture, and, after entering the capillary zone, the LNAPL migrates more slowly in the vertical direction, and disperses faster in the horizontal direction under the action of uplift force. The preferential flow not only occurs in fractured heterogeneous media, but also exists in homogeneous media in the form of finger flow, and the LNAPL with larger viscosity tends to form more narrow finger flows.