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

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.