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.
