CAREER: Decoding The Spatiotemporal Evolution of Soil Gradation under Severe Loadings: A New Paradigm for Stability Assessment of Critical Geo-Structures

该学院早期职业发展（Career）奖将支持专注于对严重载荷下颗粒土粒度演变的基本理解的研究，以及开发用于关键土工结构稳定性和适用性评估的新方法。由于自然力量和人为操纵，土壤的粒度不断变化。不希望的级配变化，如堤防和尾矿坝中承载土壤的逐步破坏，可能导致过度变形，并威胁到结构在延长使用寿命期间的安全。该研究项目将确定控制颗粒土集体破碎的原理，使新的计算工具的发展能够预测土壤级配的时空演变。这将最终促进大型土工结构更好地应对极端载荷和老化。这项研究还将与一项教育工作紧密结合，旨在为研究生提供必要的工具，使其适应气候变化，促进岩土工程本科生的保留和研究，并让第一代大学预科学生参与土木工程项目。具体而言，本研究项目将：(1)研究准静态加载下自组织在颗粒破碎中的作用；(2)研究导致可破碎土突发蠕变的微观事件链；(3)量化经历级配变化的颗粒土的力学和水力行为；(4)利用新的富级配建模范式评估世界最高尾矿坝之一的短期和长期稳定性。以下科学问题将得到解决：(1)是否存在简单的普遍规则来控制任意分级颗粒材料的破碎动力学？(2)随着时间的推移，颗粒如何集体破碎？(3)能否用统一的本构理论描述砂土的临界态行为和粒度动态？(4)颗粒土的缓慢破裂和蠕变是否对高坝的安全构成威胁？研究成果将有助于解决涉及粒度演化的广泛岩土工程和地球科学问题。这些包括桩在可破碎土壤中的渗透，铁路镇流器的破坏和退化，以及快速移动的泥石流和岩石圈剪切带的形成。该项目将使PI在极端地质力学研究方面建立长期的职业生涯，以解决基础设施，能源和环境部门的紧迫问题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This Faculty Early Career Development (CAREER) award will support research focused on the fundamental understanding of the grain-size evolution of granular soils under severe loadings and the development of new methodologies for stability and serviceability assessment of critical geo-structures. The grain size of soil constantly changes due to natural forces and human manipulation. Unwanted changes in gradation, such as the progressive breakdown of the load-bearing soil in embankments and tailings dams, can cause excessive deformation and threaten the safety of the structure over its extended service life. This research project will identify the principles that control the collective breakage of granular soils, enabling the development of new computational tools for predicting the spatial and temporal evolution of soil gradation. This will ultimately facilitate better engineering of large geostructures against extreme loading and aging. The research will also be closely integrated with an education effort aimed at equipping graduate students with the necessary toolkits for adapting geo-structures to climate change, promoting geotechnical undergraduate retention and research, and engage first-generation pre-college students in civil engineering projects.Specifically, this research project will: (1) examine the role of self-organization in grain breakage under quasi-static loading, (2) investigate the chain of micro events leading to the emergent creep of crushable soils, (3) quantify the mechanical and hydraulic behaviors of granular soils undergoing gradation shifting, (4) assess the short- and long-term stabilities of one of the world’s tallest tailings dams using the new gradation-enriched modeling paradigm. The following scientific questions will be addressed: (1) are there simple universal rules governing the crushing dynamics of arbitrarily graded granular materials?; (2) how do grains collectively break over time?; (3) can the critical-state behavior and the grain-size dynamics of sands be described using a unified constitutive theory?; (4) does the slow breakdown and creep of granular soils pose a safety threat for tall dams? The research outcomes will be useful for solving a broad class of geotechnical and geoscience problems involving grain-size evolution. These include pile penetration in crushable soils, breakage and degradation of railway ballasts, and formation of fast-moving debris flows and lithospheric shear zones. This project will enable the PI to establish his long-term career in extreme geomechanics research to address pressing issues at the interface of infrastructure, energy, and environment sectors.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.