Measurement and modeling of effective gasliquid interface in unsaturated soil.

本研究的目的是利用气体示踪剂测量非饱和土中的气液界面面积，区分流动气相和停滞气相形成的界面，并建立网络模型模拟气液驱替与界面面积变化之间的关系。我们使用庚烷，据报道，这是一个很好的示踪剂的水-空气界面面积测量。然而，事实证明，使用庚烷，我们几乎无法测量低于1×10^<-5>m^<-1>（我们感兴趣的范围）的界面面积。因此，在这一刻，我们还没有测量精确的气液界面面积与气体示踪剂。现在我们正在改进气体示踪法，例如，我们现在正在研究是否向液体中加入表面活性剂，以增强示踪气体吸附到气-液界面面积。为了区分气相流动和停滞部分，提出了一种通过分析响应曲线来测量流动和停滞气相体积的方法。在模型方面，我们建立了一个网络模型，该模型基于毛细管力并将气体包埋在水湿介质中，模拟了界面面积的变化，并将结果与液体示踪法测量的气液界面面积进行了比较。在排水过程中，模型计算结果与已有的试验结果吻合较好。

The objectives of this study is to measure the gas-liquid interfacial area in unsaturated soil by gaseous tracers, to distinguish the interface formed on flowing gaseous phase and stagnant gaseous phase, and to construct a network model to simulate the relationship between gas-liquid displacement and change in interfacial area. We used heptane, which was reported to be good tracer for water-air interfacial area measurement. However, in turned out that, with heptane, we hardly are able to measure the interfacial area below 1×10^<-5>m^<-1>, the range we were interested in. Thus, at this moment we are yet to measure the precise gas-liquid interfacial area with gaseous tracers. Now we are improving the gas tracer method, for example we now investigating if addition of surfactant into the liquid enhance the tracer gas adsorption to the gas-liquid interfacial area. For distinguishing the flowing and stagnant part of gaseous phase, we proposed a method to measure the volume of flowing and stagnant gaseous phase, by analyzing the response curve. As for the modeling, we constructed a network model, based on capillary force and incorporating gaseous entapment in a water-wet medium, and simulated the change in interfacial area and compared the results with reported gas-liquid interfacial area measured by liquid tracer methods. The model results agree with the reported experimental ones in drainage processes.