Measurement of water menisci contact angles in bulk soil samples

未来热浪和干旱等极端天气事件的频率和强度的增加可能会导致土壤润湿性的长期变化。这一点很重要，因为控制水流、土体变形和抗剪强度特性的孔隙水压力依赖于土粒表面小水弯月面的扩散。我们目前的理解是水不断扩散的条件(即土壤是可湿的)，但当水有限扩散时(即水的半月面的接触角大于零度)，我们知之甚少。为了预测具有可变润湿性的土壤(通常是高有机碳含量的土壤)的工程性质，必须确定土壤润湿性与孔压之间的关系。非饱和土力学计算孔压的方法有多种。然而，现有的土壤润湿性方法是为土壤科学应用(如农业)而开发的，不能直接适用于地面工程。例如，几种方法使用单层颗粒来测量水的半月面接触角，但这不适用于土力学，因为测试是在大样本中进行的。需要资金前往德国汉诺威莱布尼茨大学土壤科学研究所的约尔格·巴赫曼教授实验室(土壤湿润性测量的世界领先者)，学习现有的土壤科学方法，并将其应用于地面工程。这将为未来的研究提供基础，在这些研究中，液体与土壤颗粒表面的相互作用是重要的。应用领域包括地质环境和岩土工程、地球表面过程(遭受野火侵袭的斜坡上的侵蚀和滑坡)、土壤碳封存、新材料的开发(颗粒状、防水性)和颗粒表面过程(长期影响)。

The increase in the frequency and intensity of extreme weather events in the future such as heat waves and droughts is likely to induce long lasting changes of soil wettability. This is important because pore water pressure, which controls water flow, the deformation and shear strength characteristics of soils, depends on the spreading of small water menisci at the surface of the soil particles. Our current understanding is for conditions where the water spreads continuously (i.e. the soils are wettable), but little is known when water has limited spreading (i.e. the water menisci have contact angles greater than zero degrees). To predict the engineering behaviour of soils with variable wettability (frequently those with high organic carbon content), the relation between soil wettability and pore water pressure has to be determined. There are several methods for pore water pressure from unsaturated soil mechanics. However, the existing soil wettability methods have been developed for soil science applications (e.g. agriculture) and are not directly suitable for ground engineering. For instance, several methods use a single layer of particles to measure the water menisci contact angles but this is not appropriate to soil mechanics where testing is conducted in bulk samples. Funds are requested to travel to Prof. Jörg Bachmann laboratory (world leader on the measurement of soil wettability) at the Institute of Soil Science, Leibniz University Hannover, Germany to learn and adapt the existing soil science methods to ground engineering. This will provide the basis for future studies where the interaction of liquids with the surface of soil particles is important. Applications are in geoenvironmental and geotechnical engineering, earth surface processes (erosional and landsliding in slopes subjected to wildfires), soil carbon sequestration, development of new materials (granular, water repellent) and particle surface processes (long term effects).