Transient Flow-Induced Soil Failures of Coastal Structures

在风暴潮期间，瞬时流体压力可能会导致严重的土体破坏，包括瞬时冲刷、斜坡失稳、滑动、地下渗漏、底部隆起、内部侵蚀和液化。该项目的目标是(1)开发先进的数值工具来研究海岸建筑物不同的瞬时水流引起的土体破坏模式，(2)建立每种模式的破坏函数并确定破坏模式之间的关系，(3)量化水流和土壤变量对受风暴潮影响的典型海岸建筑物的性能的影响。我们将扩展由Pi Young开发的完全耦合的波浪-泥沙输运模型，以模拟任意几何形状上的近场波浪爬升和崩塌以及与之相关的瞬时冲刷。将考虑底部摩擦和渗透率的影响、泥沙输送引起的动量转移、床面形态的变化以及波浪破碎和与多孔介质接触造成的能量耗散。将包括概率模型来表示流入边界处的有效波高、峰值周期和平均方向的场。为了模拟海岸建筑物由水流引起的土体瞬变破坏，有限体积流动求解器将与有限元程序DYNAFLOW完全耦合，DYNAFLOW是由Pi Prevost共同开发的有限元程序。DYNAFLOW配备了非线性、非弹性、多屈服本构模型(已通过现场和离心机实验验证)，用于模拟动态诱导的超孔隙水压力积累以及由此导致的非均质土材料的软化和/或硬化。基于非线性破坏力学的X-有限元方法将被用来模拟土体系统中滑移破坏的扩展。我们将研究不同组的无量纲波浪和土壤变量对理想化和特定场地(Ponchat rain的堤防防洪墙系统的概念表示)结构和水深测量的动态响应的影响。最后，我们将调查当前设计建议的充分性，并开发新的/改进的失效函数和失效关系，为基于可靠性的海岸结构现实设计提供必要的工具。这个项目的一个重要组成部分是三位共同参与的、具有水文灾害、固体和流体动力学专业知识的皮？S的跨学科合作，以及来自美国陆军工程兵团的顾问小组的参与，他们共同拥有解决问题的关键专业知识。我们的教育目标是：(I)创造知识，并向学术界、工业界和政府部门传播知识；(Ii)教育新一代科学家和工程师，使他们了解风暴工程的关键问题；以及(Iii)增加少数族裔和贫困学生对科学和工程学的参与。为了实现这些目标，我们将：(1)与伍德罗·威尔逊公共事务学院合作举办多学科系列研讨会，以更好地教育公众风暴工程的重要性；(2)与团队成员和顾问小组定期举行会议；(3)通过独立研究项目、高级论文和暑期实习将本科生纳入研究；以及(4)通过普林斯顿大学的外联项目，包括NSF赞助的REU(通过PRISM在普林斯顿协调)和普林斯顿大学材料研究所，鼓励高中生和本科生参与研究。

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.