Flow and transport in the vadose zone: Soil atmosphere boundary and capillarity effects

在过去的几十年里，我们理解和模拟包气带(地下水位以上的地下)中的流动和输送过程的能力有了很大提高。文献中的证据表明，已经发展了大量的概念模型，这些概念模型可以转化为数值模型来研究包气带内的瞬时变饱和水流、热和溶质运移。本研究旨在发展和验证现有的概念和数值模式：(1)物理和化学过程的耦合，以及(2)表层和次表层过程的整合。本研究的关键是通过界面现象量化土壤-大气边界和浓度相关的毛细管对包气带内流动和输运的影响。这些现象对许多岩土工程和岩土环境设计都有相当大的影响。这项研究将加深我们对包气带中耦合、非线性、物理和化学过程的理解，从而提高我们的设计能力。建议通过若干相关研究来实现这一目标，每项研究都有自己的具体目标。 设计应用1.本研究旨在量化气候变化对膨胀土(又称膨胀土和收缩土)行为的影响。这些土壤经历了很大的体积变化，土壤水分也发生了变化。气候是影响膨胀土性状的主要因素。加拿大大草原的大部分人口聚居区被厚厚的冰川沉积物覆盖，这些沉积物本质上是广阔的。里贾纳市和温尼伯市的浅层地基和基础设施(地下管道)长期以来一直受到膨胀土膨胀和收缩的影响，将从这项研究中受益。 设计应用2.随着气候变化对现有水资源施加更大压力，使用灰水(GW)灌溉和补给含水层正变得越来越普遍。GW是指洗衣和厨房产生的家庭废水，含有大量的表面活性剂。毛细作用是使土壤保持水分并调节其运动的主要力量。GW通过改变表面张力和接触角等界面性质来影响毛细作用。这一研究将加深我们对GW在包气带中流动和输运的基本过程的理解。 设计应用3.土壤覆盖是任何废物管理设施的重要组成部分。土壤覆盖物可以看作是位于大气和下层废物之间的一个薄薄的界面。它们将有毒废物从大气中分离出来，而气候是主要的设计变量。预计它们将在很长一段时间内发挥作用，并极有可能受到气候变化的影响。这项研究的目的是通过整合地表和地下过程来制定土壤覆盖的设计指南。

Over the past few decades our ability to understand and model flow and transport processes in the vadose zone (subsurface above the groundwater table) has increased considerably. Evidence from the literature suggests, that a large number of conceptual models have been developed which can be translated to numerical models to study the transient variably saturated water flow, heat and solute transport in the vadose zone. This research aims to develop new and validate existing conceptual and numerical models for: (1) coupling of physical and chemical processes, and (2) integration of surface and subsurface processes. The crux of this research is to quantify the effect of soil-atmosphere boundary and concentration dependent capillarity on flow and transport in the vadose zone via interfacial phenomena. These phenomena have considerable influence on many geotechnical and geoenvironmental designs. This research will improve our understanding of the coupled, non-linear, physical and chemical processes operative in the vadose zone to improve our design capabilities. It is proposed to achieve this goal via a number of related studies, each with its own specific objectives. Design application 1. This study aims to quantify the effect of climate change on behavior of expansive soils also known as swelling and shrinking soils. These soils go through large volume change, with changes in soil water content. Climate is the primary factor that affects the behavior of expansive soils. Most of the populated area of prairie Canada is covered with thick glacial deposits that are expansive in nature. Shallow foundations and infrastructure (buried pipelines) in the city of Regina and Winnipeg have a long history of being affected by the swelling and shrinkage of expansive soils and will benefit from this research. Design application 2. As the climate change puts more pressure on the existing water resources, the use of grey water (GW) for irrigation and aquifer recharge is becoming increasingly common. GW refers to household wastewater form laundry and kitchen and contains large quantities of surfactants. Capillarity is the primary force that enables the soil to retain water and regulates its movement. GW effects capillarity by changing the interfacial properties such as surface tension and contact angle. This research will enhance our understanding of the fundamental processes in the flow and transport of GW in vadose zone. Design application 3. Soil covers are an important part of any waste management facility. A soil cover can be viewed as a thin interface placed between the atmosphere and the underlying waste. They separate the toxic waste from the atmosphere and climate is a primary design variable. They are expected to be functional for very long periods and are highly likely to be affected by climate change. The objective of the research is to develop design guidelines for soil covers by integrating the surface and subsurface processes.