Evaluation of piled-supported structures under extreme scour conditions

冲刷是一种由水流和波浪引起的土壤侵蚀过程，它会影响自然和人工特征，如海滩、堤坝和地基。冲刷不仅会导致地基的土体支撑丧失，还会导致地基构件的劣化，从而影响结构的完整性，威胁公共安全。冲刷是一个世界性的问题。它已成为桥梁失效的主要原因。根据Lagasse等人（2007）的研究，美国60%的桥梁损坏是冲刷造成的。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，结构和岩土知识。广泛的研究工作集中在冲刷深度预测、冲刷保护和冲刷监测技术上。也有许多研究集中在冲刷条件下桩基或桥梁的性能。然而，关于冲刷过程中出现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，因为覆盖层在冲刷过程中被移除。这一过程导致了土壤应力历史和剩余土壤性质的变化。在检查桥梁或海上结构的冲刷敏感性时，土壤应力历史的变化通常被忽略。此外，另一种简化方法往往是忽略冲孔几何特性的变化。除了岩土工程问题之外，从结构工程的角度来看，在建模中还存在过度简化的问题。例如，对桥梁性能的评估通常是通过只分析桥梁的一个组成部分而忽略其他组成部分来完成的，或者通过使用简化的基础边界条件来分析整个桥梁。***本研究计划的目的是通过理论推导和数值模拟对上述问题提供全面的理解。具体目标是：***1。考虑土体应力历史和冲刷孔特性变化的群桩轴向和侧向荷载评价；***2。开发了冲刷条件下的桩分析新程序，该程序允许考虑土壤应力历史和冲刷孔特性的影响。* * * 3。考虑到土壤、基础和上层建筑的相互作用，对受冲刷的结构进行综合分析过程的发展。***我的研究项目的长期目标是改进桩和桩支撑结构在极端冲刷下的设计和分析程序，为基础设施面对自然灾害的可持续性和弹性做出贡献。**

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. **