Coupled Thermo-Hydro-Mechanical Behavior of Soils Subjected to Freeze-Thaw Cycles

季节性冻土约占地球表面积的55%。气温上升，特别是在高纬度地区，导致地面温度上升，加剧了永久冻土的退化。对于季节性冻土地区的民用基础设施的安全和经济设计来说，对冻土的特性有很好的了解是至关重要的。考虑到最近在北极圈附近发现了化石燃料(如天然气水合物)，以及在这些地区发展新基础设施的相关需要，这一方面尤其相关。此外，人工冻土技术已成为建造更深、更快、更大和更复杂的岩土结构(如大城市地区的隧道)的非凡盟友。然而，最近与这种方法相关的一些施工问题表明，有必要更好地了解与冻土行为的复杂性质相关的基本方面。本项目的研究成果将纳入本科生和研究生课程。该项目为研究生和本科生提供了新的岩土工程技术技能和更好地了解土壤冻融循环及其对环境和已建基础设施的影响的机会。该项目将推进热力地质学的一般领域，对涉及土壤遭受冻融循环的问题作出贡献。该项目的总体目标是促进当前对冻土行为的理解。特别是，将追求以下具体目标：(1)更好地了解与冻土行为有关的主要特征，包括冻土退化、冻融循环的影响、应力历史的影响以及土壤-结构与水相转变过程中的水量变化之间的相互作用；(2)提供与冻土行为有关的高质量实验数据，包括各种应力水平、温度、应力历史和冻土退化情景，这将有助于扩大这一领域目前的数据库；以及(3)开发先进的本构和数值代码，以处理冻土在复杂的冻融循环和加载条件下的问题。为了实现这些目标，将进行实验和数值研究相结合的方案。研究成果将通过科学出版物和专门的网站传播。这项研究与NSF的新北极航行计划相一致。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Seasonally frozen soils occupy approximately 55 percent of the earth's total surface land. Rising air temperatures particularly in the upper latitudes are causing an increase in ground temperatures, intensifying permafrost degradation. A good understanding of the behavior of frozen soils is critical for safe and economical design of civil infrastructure in regions seasonally exposed to freezing temperatures. This aspect is particularly relevant considering the recent discovery of fossil fuels (e.g., gas hydrates) near the Arctic Circle, with the associated needs of developing new infrastructure in these regions. Moreover, artificial ground freezing technique has become an extraordinary ally for building deeper, quicker, bigger and more complex geotechnical structures (e.g., tunnels in large urban areas). However, some recent construction issues associated with this methodology have shown the need to gain a better understanding of the fundamental aspects associated with the complex nature of frozen soil behavior. The outcomes of the research contributions in this project will be incorporated into undergraduate and graduate curricula. The project offers opportunities for graduate and undergraduate students novel technical skills in geotechnical engineering and a better understanding of the soil freeze-thaw cycles and its impact on the environment and built infrastructure. The project will advance the general area of thermal geotechnics, with contributions towards problems involving soils subjected to freeze-thaw cycles. The overarching goal of this project is to advance the current understanding of frozen soil behavior. Particularly, the following specific objectives will be pursued: (i) gain a better understanding of the key features associated with the behavior of frozen soils, including permafrost degradation, the effect of freeze-thaw cycles, the impact of stress history, and the interaction between the soil-fabric and the changes in water-volume occurring during water-phase transformations; (ii) produce high-quality experimental data related to the behavior of frozen soils including a variety of stress levels, temperatures, stress history, and permafrost degradation scenarios, which will contribute to expanding the current database in this area; and (iii) develop advanced constitutive and numerical codes to tackle problems involving frozen soils subjected to complex freeze-thaw cycles and loading conditions. A combined experimental, and numerical investigation program will be conducted to achieve these objectives. Research findings will be disseminated through scientific publications and a dedicated website. This research aligns with NSF's Navigating the New Arctic program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.