Deformation and Failure Behavior of Soils under Erosion

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Soil erosion is the main cause of failure for dams and levees and can have disastrous consequences, such as the catastrophies in New Orleans in 2006 and in Iowa in 2008. According to the latest Report Card for America?s Infrastructure, issued in 2009 by the American Society of Civil Engineers, dams and levees are in the D minus range. Many dams and levees are structurally deficient and barely above failing. The risk of internal erosion in earth structures becomes a critical issue. The main goal of this research is to address the mechanics of deformation and instability caused by internal erosion. A stress-strain model will be developed that will (1) consider the micro-scale mechanism of pore collapse, and (2) account for the evolution of internal structure such as specific volume and gradation. T his stress strain law will be implemented into a finite element method capable of analyzing earth structure under erosion. This research work will be conducted in collaboration with Ecole Centrale de Nantes, where an experimental soil erosion research program is currently in progress. The collaborator will provide experimental results necessary for this research.The scientific significance of this research is twofold: (1) The investigation will lead to a new direction of damage mechanics, in which the damage is not caused by external load, but rather by a loss of part of the material constituents. (2) The micromechanics modeling method, in which the behavior is derived from postulated mechanisms, will provide insight into the underlying physical processes. The study will also bring the mathematical expressions of soil fabric (such as voids and particle size distribution) into the physics of constitutive models, which is of core importance to a constitutive theory for soil.The broader impacts will be as follows: (1) Integrate research and education by incorporating the research results and activities into graduate courses on sear strength and soil mechanics. (2) Broaden participation and enhance diversity by involving undergraduate students from the Northeast Alliance Program at the University of Massachusetts, an NSF funded program aimed at recruiting underrepresented minority students into doctoral study in science and engineering. (3) Enhance infrastructure for research and education by establishing international collaboration with the Civil Engineering Laboratory of Nantes.Saint-Nazaire. (4) Develop a defense against natural disasters such as landslides and floods through the enhancement of civil engineering infrastructure.