CAREER: Mobility of Unfrozen Water in Frozen Soil

职业：冻土中未冻水的流动性

• 批准号: 1147806
• 负责人: Margaret Darrow
• 金额: $ 40.3万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1147806&HistoricalAwards=false
• 关键词: CAREER; Mobility; Unfrozen; Water; Frozen

This Faculty Early Career Development (CAREER) award supports research that will improve our understanding of how frozen ground behaves as it interacts with thermal changes in the surrounding environment. A key element in understanding soil freezing and thawing processes is the ability to predict the mass fraction and mobility of unfrozen water (that is, how much water remains liquid at below-freezing temperatures within frozen soils, and how it moves). Historically, microscale phenomena associated with unfrozen water has been challenging to measure and poorly understood. This research uses an innovative combination of state-of-the-art measurement techniques to quantify relationships among hypothesized key variables in soil freezing and thawing processes, namely unfrozen water content and mobility, soil zeta potential (a parameter related to mineral surface charge), and soil micro-fabric. Specifically, the PI will (1) measure mass and molecular mobility of unfrozen water in frozen cation-treated soils using pulsed nuclear magnetic resonance (NMR) methods; (2) correlate these with measurements of soil micro-aggregate formation and micro-fabric using X-ray computed tomography (CT) scanning, X-ray diffraction (XRD), and scanning electron microscopy (SEM) methodologies; and (3) correlate these measurements to zeta potential of cation-treated soil particles at sub-freezing temperatures. Students recruited from the Alaska Native Science and Engineering Program (ANSEP) will participate in this CAREER research and in K-8 outreach through a hands-on geotechnical engineering module delivered to middle school-aged students.The ability to accurately predict heat and mass balance of frozen soil systems, frozen soil strength, and frost heave magnitude - all of which depend on unfrozen water - will support planning for permafrost response to climate change, and will facilitate more efficient and economic engineering design for cold regions. Results from this CAREER research may be used to improve heat and mass transport models, frost heave models, and models of frozen soil creep by incorporating enhanced unfrozen water content functions, which will account for unfrozen water mobility and its dependence on soil-specific physicochemical properties. The improved models will have far-reaching effects, including: contributing to the scientific community studying methane release from degrading permafrost; serving as planning tools for Arctic communities that must relocate due to unstable permafrost; increasing the analysis accuracy of unstable slopes in frozen ground; resulting in more cost-effective designs accompanied by less structural damage and safety risks for projects such as buried chilled gas pipelines; and predicting frost heave susceptibility and magnitude more accurately, which will support design of safer, more durable roads in cold regions.In terms of education, involving ANSEP students in this research will encourage underrepresented student groups to become engineering professionals with strong outreach skills, who can return to rural Alaska to inspire the next generation of engineers. Increasing the involvement of Alaskan Native students in frozen ground engineering will result in a stronger, highly-trained workforce, capable of addressing geotechnical problems unique to the Arctic, which is critical for the long-term viability of their communities and for the successful development of the Arctic, the next frontier in energy resource development. Exposing middle school-aged students to hands-on engineering activities and to problems germane to their local environment will promote an early interest in engineering that can segue into an engineering career.

这项教师早期职业发展（职业）奖支持了研究，这将提高我们对冷冻地面在与周围环境中的热变化相互作用时的表现的理解。 理解土壤冻结和解冻过程的关键要素是能够预测未冻结水的质量分数和迁移率（也就是说，在冷冻土壤中的低于冰冻的温度下，多少水仍然是液体的，以及它的移动方式）。 从历史上看，与未开发水相关的微观现象在衡量和了解不足方面具有挑战性。 这项研究使用了最先进的测量技术的创新组合来量化在土壤冷冻和解冻过程中假设的关键变量之间的关系，即没有水分的水分和迁移率，土壤Zeta电位（与矿物表面电荷相关的参数）以及土壤微生物。 具体而言，PI（1）使用脉冲核磁共振（NMR）方法测量冷冻阳离子处理的土壤中未冻结水的质量和分子迁移率； （2）将它们与使用X射线计算机断层扫描（CT）扫描，X射线衍射（XRD）和扫描电子显微镜（SEM）方法相关联的土壤微型聚集形成和微型效果； （3）将这些测量与阳离子处理的土壤颗粒在亚冻结温度下的潜力相关联。 从阿拉斯加本土科学与工程计划（ANSEP）招募的学生将通过交付给中学生的怪异技术工程模块参加这项职业研究和K-8外展活动，准确预测冻结的土壤强度，以及依赖于实现的范围的水位，可以准确预测热量和质量平衡的能力 - 寒冷地区更高效，更经济的工程设计。 这项职业研究的结果可用于改善热量和质量传输模型，霜冻堆模型以及冻结土壤蠕变的模型，通过纳入增强的未透明的水含量功能，这将构成水的迁移率及其对土壤特异性物理化学特性的依赖。 改进的模型将产生深远的影响，包括：为科学界研究甲烷释放而降解多年冻土的释放；作为北极社区的规划工具，由于多年冻土不稳定而必须搬迁；提高了冷冻地面上不稳定斜率的分析精度；导致更具成本效益的设计，伴随着掩埋的冷藏燃气管道等项目的结构损害和安全风险较小；并更准确地预测霜冻的易感性和幅度，这将支持在寒冷地区的更安全，更耐用的道路的设计。在教育方面，参与这项研究的ANSEP学生将鼓励代表性不足的学生群体成为具有强大的外展能力的工程专业人士，他们可以返回阿拉斯加农村地区以启发下一代工程师。 增加阿拉斯加土著学生参与冷冻地面工程的参与将导致更强大，训练有素的劳动力，能够解决北极独有的岩土技术问题，这对于其社区的长期可行性以及对北极的成功发展至关重要，这是能源资源开发的下一个领域。 将中学学生暴露于实践工程活动，并向他们的当地环境造成问题，这将促进对工程学的早期兴趣，从而使工程职业成为工程职业。