Unsaturated soil geotechnics / linking with China

岩土工程是研究地下建筑，如隧道，地基和斜坡，以及它们如何影响环境。岩土工程师必须确定现有建筑物和拟议新工程的移动情况并评估其稳定性。要做到这一点，就需要使用计算机模拟，模拟实际情况。为了获得准确的答案，工程师将复杂的关系纳入这些模型中，这些关系定义了物理问题中的土壤如何对载荷的应用做出反应。土壤是有趣的材料，因为它们的行为也受到土壤孔隙之间水的运动的影响。随着水压的增加，它会把土壤颗粒推开，土壤的强度就会降低。土力学的历史（工程师对土壤特性的研究）很短。目前工程师常用的大多数想法都是在世纪中期发展起来的。这些想法的一个特点是假设水完全填充土壤中的孔隙（称为饱和）。然而，现在人们认识到，大多数真实的土壤的孔隙中除了水之外，还有空气，这对土壤的性状有重大影响。这就是非饱和土力学，这是一个主要的研究领域，还有很多研究要做。达勒姆（和其他地方）的工程学者正在开发非饱和土行为的新模型。模型是指以计算机程序可以理解的形式对土壤行为的数学表示。要做到这一点，需要进行实验室测试，以确定行为特征。例如，当我们把水加到未膨胀的土壤样本中时会发生什么（它会塌陷，但何时，如何塌陷？）在测试之后，我们需要将观察到的行为转换为数学模型。然后我们需要确保计算机模型有效运行，以便工业工程师可以使用它们。我们计划派遣的访问中国学术界的团队具有上述光谱的专业知识，即通过计算机建模和应用的非饱和土的基本原理。我们特别感兴趣的是使用这些模型来改善污染土地的修复，这往往是在一个不饱和的状态。暴雨引发的滑坡也是非饱和土壤特性的一个特征。

Geotechnical engineering is the study of constructions in the ground, such as tunnels, foundations and slopes, and how they affect the environment. Geotechnical engineers have to determine movements and assess stability, of existing constructions and proposed new works. To do this requires the use of computer simulations where the physical situation is modelled. To obtain accurate answers, engineers incorporate into these models complex relationships that define how the soils in the physical problem react to the application of loads. Soils are interesting matrerials to work with, as their behaviour is affected also by the movement of water between the soil pores. As the water pressure rises it pushes the soil particles apart and the strength of the soil reduces. The history of soil mechanics (as the study of soil behaviour by engineers is known) is quite short. Most of the ideas currently used routinely by engineers was developed during the middle of the 20th century. A feature of these ideas is the assumption that water entirely fills the pores in soils (known as saturation). It is now recognised, however, that most real soils have air in additon to water in the pores, and this has a major influence on the behaviour. This is unsaturated soil mechanics, an area of major interest with much research still to be done.Engineering academics at Durham (and elsewhere) are developing new models of unsaturated soil behaviour. By models we mean the mathematical representation of the behaviour of a soil, in a form that can be understood by a computer program. To do this requires laboratory testing, to identify features of behaviour. For instance, what happens as we add water to a sample of unstaurated soil (it collapses, but when, and how?) Following testing we need to transform the observed behaviour into a mathematical model. We then need to make sure the computer models run efficiently so that engineeris in industry can make use of them.The team we are planning to send to visit academics in China has expertise across the specturm putlined above, i.e. the fundamentals of unsaturated soils, through the computer modelling and onto applications. We are particularly interested in using these models to improve remediation of contaminated land, which is often in an unsaturated state. Landslides triggered by heavy rain are also a feature of unsaturated soil behaviour.