Collaborative Research: A Fundamentals-based Paradigm for Expansive Soil Classification

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Damage and litigation costs from construction of buildings, roads, and bridges, on expansive soils total billions of dollars each year in the US alone, yet the current state of mitigation practice still heavily relies on antiquated, uncertain, and highly empirical site characterization methods. A more systematic and fundamentally sound approach for expansive soil classification is required to alleviate the severe economic and social burden of damages resulting from these materials. The new paradigm in this project for soil classification is viewed as central to solving current global societal and environmental challenges, including energy and resource needs, infrastructure development, environmental protection and enhancement, and protection and recovery from natural disasters. The framework will allow designers to more effectively quantify site variability by allowing a larger and more diverse suite of samples to be tested in a short amount of time. Improved basic understanding of expansive clays will impact the tremendously broad range of applications where they have found use, including environmental applications such as waste containment, filtration and membranes, and as industrial adsorbents. Activities will be integrated with the research to capitalize on the collaborative nature of the project, including a summer exchange program for students at the University of Wisconsin (UW) and the Colorado School of Mines (CSM) and education/diversity initiatives implemented through existing programs at UW and CSM. A hands-on training workshop will be organized to disseminate the new soil classification system to the practicing geotechnical engineering community.The goal of this project is to modernize geotechnical engineering practice by developing a new paradigm for expansive soil characterization based on fundamental soil properties and behavior. Two distinct physicochemical mechanisms responsible for clay swelling behavior - crystalline swelling and osmotic swelling - will form the basis of the new framework. The approach in this project explicitly differentiates these mechanisms to glean specific information about fundamental clay properties including specific surface area and cation exchange capacity and to classify expansive clays using independent mineralogy and pore fluid chemistry criteria. Modern experimental approaches, including automated measurements of water vapor sorption isotherms and soil shrinkage curves, will replace historical index measurements (e.g. Atterberg Limits) in the new expansive soil classification system.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.