Evaluation of piled-supported structures under extreme scour conditions

冲刷是由水流和波浪引起的土壤侵蚀过程，它会影响自然和人为特征，如海滩，堤坝和地基。 冲刷不仅会导致地基的土壤支撑丧失，而且会导致地基构件的劣化，从而损害结构的完整性并威胁公共安全。 冲刷是一个世界性的问题。 它已成为导致桥梁破坏的主要因素。 根据Lagasse等人（2007年）的研究，美国60%的桥梁故障是由冲刷造成的。 冲刷条件下的结构行为是一个多学科的主题，需要使用水力，结构和岩土工程知识。 冲刷深度预测、冲刷防护和冲刷监测技术是冲刷研究的重点。 也有一些研究集中在冲刷条件下桩基或桥梁的性能。 然而，关于冲刷过程中产生的岩土工程问题的研究报道很少。 从岩土工程的角度来看，冲刷是一个卸载到未冲刷土壤（或剩余土壤）的过程，因为在冲刷过程中覆盖层被移除。 这一过程导致了土体应力历史的变化和剩余土体中的土性变化。 在检查桥梁或海洋结构物的冲刷敏感性时，通常忽略土壤应力历史的变化。 此外，另一种简化往往是通过忽略的变化，以孔的几何属性。 除了岩土工程问题之外，在建模中也存在过度简化的问题，这些问题通常是从结构工程的角度进行的。 例如，桥梁行为的评估通常是通过仅分析桥梁的一个部件而忽略其他部件来完成的，或者通过使用简化的基础边界条件分析整座桥梁来完成的。 本研究计划的目标是通过理论推导和数值模拟，全面了解上述问题。 具体目标是： 1.考虑冲刷事件中土壤应力历史和钻孔特性变化的轴向和横向受载群桩的评估 2.冲刷条件下桩分析的新程序的开发，该程序考虑了土壤应力历史和桩孔特性的影响。 3.考虑土壤、基础和上部结构相互作用，以整体方式开发受冲刷结构的综合分析过程。 我的研究项目的长期目标是改善桩和桩支撑结构的设计和分析程序，受到极端冲刷，并有助于基础设施的可持续性和弹性面临的自然灾害。

Scour is a process of soil erosion caused by currents and waves, which affects natural and man-made features such as beaches, levees, and foundations. Scour can result in not only the loss of soil supports to foundations, but also the deterioration of the foundation elements, therefore compromising the structural integrity and threatening public safety. Scour is a worldwide problem. It has been the predominant factor responsible for the bridge failures. According to Lagasse et al. (2007), 60% of bridge failures in the United States resulted from scour. Structural behaviors under scour conditions are a multidisciplinary topic requiring the use of hydraulic, structural, and geotechnical knowledge. Extensive research efforts have been focused on the prediction of scour depths, scour protection, and scour monitoring technologies. There are also a number of studies focusing on the performance of pile foundations or bridges under scour conditions. However, very few studies have been reported on the geotechnical problems arising during scouring process. From a geotechnical perspective, scour is a process of unloading to the unscoured soils (or remaining soils) as the overburden is removed over the course of scour. This process results in the change to soil stress history and the soil properties in the remaining soils. When examining the scour susceptibility of bridges or offshore structures, the changes to soil stress history are typically neglected. Moreover, another simplification is often made by ignoring the changes to scour-hole geometric properties. In addition to geotechnical problems, there are over-simplifications in modeling that are often made from a structural engineering perspective. For example, evaluation of bridge behavior is often accomplished either by analyzing only one component of a bridge while ignoring the other components, or by analyzing an entire bridge using simplified boundary conditions for the foundations. The objectives of this research program are to provide a comprehensive understanding of the above-mentioned concerns using theoretical derivation and numerical modeling. The specific targets are: 1. Evaluation of axially and laterally loaded group piles considering changes to soil stress history and scour-hole properties in a scour event; 2. Development of a new program for pile analyses under scour conditions, which allows for considering effects of soil stress history and scour-hole properties. 3. Development of an integrated analysis process for a structure subjected to scour in a holistic manner considering soil, foundation, and superstructure interactions. The long-term goal of my research program is to improve the design and analysis procedures for piles and pile supported structures subjected to extreme scour, and contribute to sustainability and resilience of infrastructures facing the natural hazards.