Transient Flow-Induced Soil Failures of Coastal Structures

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During a storm surge, transient fluid pressures can lead to serious soil failures, including transient scour, slope instability, sliding, underseepage, bottom heave, internal erosion, and liquefaction. The objectives of this project are to (1) develop advanced numerical tools to investigate the different modes of transient flow-induced soil failures of coastal structures, (2) develop failure functions for each mode and identify relationships between failure modes, and (3) quantify the influence of flow and soil variables on the performance of typical coastal structures subject to storm surges. We will extend a fully coupled wave-sediment transport model developed by PI Young to simulate near-field wave runup and rundown, and associated transient scour, over arbitrary geometries. The effects of bottom friction and permeability, momentum transfer due to sediment transport, changes in bed morphology, and energy dissipation due to wave breaking and contact with porous media will be considered. Probabilistic models will be included to represent the fields of significant wave height, peak period, and mean direction at the inflow boundary. To simulate transient flow-induced soil failures of coastal structures, the finite volume flow solver will be fully coupled with DYNAFLOW, a finite element program developed by co-PI Prevost over the last twenty years. DYNAFLOW is equipped with nonlinear, inelastic, multi-yield constitutive models (which have been validated with field and centrifuge experiments) to simulate dynamically induced excess pore water pressure buildup and resulting softening and/or hardening of inhomogeneous soil materials. An efficient X-FEM approach based on nonlinear failure mechanics will be employed to model slip failure propagation in soil systems. We will examine the influence of different groups of non-dimensional wave and soil variables on the dynamic response of idealized and site-specific (conceptual representation of the levee-flood wall system at Lake Ponchatrain) structure and bathymetry. Finally, we will investigate the adequacy of current design recommendations, and develop new/improve failure functions and failure relationships to provide the necessary tools for realistic reliability-based design of coastal structures.An essential ingredient of this project is the cross-disciplinary collaboration of the three co-PI?s with expertise on hydrological hazards, solid and fluid dynamics, and the participation of an advisory panel from the US Army Corps of Engineers, together possessing critical expertise for tackling the problem. Our educational goals are to: (i) create and disseminate knowledge to the academic, industrial and government sectors; (ii) educate a new generation of scientists and engineers about problems critical to storm engineering; and (iii) increase participation of minority and underprivileged students in science and engineering. To implement these goals, we will: (1) organize multi-disciplinary seminar series in collaboration with the Woodrow Wilson School of Public Affairs to better educate the public about the importance of storm engineering; (2) hold regular meetings with team members and advisory panel; (3) include undergraduates in the research through independent research projects, senior theses, and summer internships; and (4) encourage involvement of high school and undergraduate students through outreach programs at Princeton, including the NSF-sponsored REU (coordinated at Princeton through PRISM) and the Princeton University Materials Institute.