NEESR-II: Evaluation of Seismic Levee Deformation Potential by Destructive Cyclic Field Testing

NEESR-II：通过破坏性循环现场试验评估地震堤坝变形潜力

• 批准号: 0830081
• 负责人: Scott Brandenberg
• 金额: $ 37.5万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-10-01 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0830081&HistoricalAwards=false
• 关键词: NEESR; II; Evaluation; Seismic; Levee

The Sacramento-San Joaquin Delta levees are critical components of California?s water distribution system. The Delta supplies fresh water to 22 million people in southern and central California as well as eastern portions of the San Francisco Bay area and directly supports $400 billion/year of economic activity within the State of California. The ?islands? circumscribed by the network of levees are commonly 3 to 5 meters below sea level, and are protected by only about 1 to 1.5 meters of freeboard at high tide. A breach in a levee causes water from the channel to flow into the island thereby inundating farmland and wildlife habitat, and drawing saline water from the San Francisco Bay into the Delta. This is a potentially catastrophic scenario, as saline contamination could halt water delivery to central and southern California, removing the sole water source for many communities. This scenario is unlikely in the event of an individual levee breach caused by burrowing animals and other local hazards because the existing emergency response system can respond to a single breach within a matter of hours and affect repair within a matter of weeks. On the other hand, seismic hazard is an extraordinary threat because of the potential for multiple simultaneous breaches inundating many islands within the Delta. Such widespread system failure has been forecast to cause up to 28 months of time during which fresh water deliveries from the Delta would not be possible. Some in fact question whether such a sequence of breaches might permanently change the regional morphology such that either alternative water sources would need to be identified or major sectors of the California economy/population would need to be reconfigured or relocated. The influence of earthquake shaking on the behavior of the levees is uncertain because the cyclic deformation potential of the underlying peaty organic soils not well understood, and there is an urgent need to investigate the behavior of these materials.Intellectual Merit and Scope: This award will support full-scale testing of an existing earth embankment (very similar in geometry to a levee, but not currently holding water) to investigate the in situ deformation potential of peaty organic foundation soils under realistic stresses and boundary conditions. The test conditions and instrumentation will be designed to measure the deformation mechanisms that can result in a critical loss of freeboard leading to a breach. Data of this sort is essential for the development of more rational analysis tools for assessing the seismic vulnerability of levees. The field testing will be supplemented by an extensive laboratory testing program to further investigate key material response characteristics such as soil strength loss and volume reduction caused by shaking. The improved knowledge of levee seismic vulnerability will be broadly applicable wherever these earth structures are founded on organic soils. Testing activities will be closely coordinated with engineers at the California Department of Water Resources to identify a suitable site. Insights gained from this project could fundamentally alter the manner in which Delta seismic risk is assessed and retrofit decisions are made. Broader Impacts: The most important societal impact of this research will be improvement of seismic risk assessment in the Delta, which in turn will result in better informed retrofit and/or construction decisions and a water delivery system that is more likely to maintain functionality during and following earthquake shaking. This award will also support development of education modules that leverage NEES resources to contribute to the broader NEESinc goals for education, outreach and training (EOT). The modules will teach about the current water delivery system, the network of levees in the Delta, the link between water delivery and the levee network, the engineering properties of these levees, the potential seismic failure mechanisms of the levees, and the consequences on the availability of water for drinking and irrigation. Included with the modules will be a study guide containing suggestions regarding implementation of the modules at different levels (i.e., undergraduates and K-12). Data from this project will be made available through the NEES data repository (http://www.nees.org)

萨克拉门托-圣华金三角洲堤坝是加州的重要组成部分？水分配系统。三角洲为加州南部和中部以及弗朗西斯科湾区东部的2200万人提供淡水，并直接支持加州每年4000亿美元的经济活动。什么？岛屿？由堤坝网围成的海平面一般低于海平面3至5米，在涨潮时只有约1至1.5米的干舷保护。 堤坝的一个缺口导致水从海峡流入岛屿，从而淹没农田和野生动物栖息地，并将盐水从旧金山弗朗西斯科湾引入三角洲。这是一个潜在的灾难性情景，因为盐水污染可能会停止向加州中部和南部供水，从而消除许多社区的唯一水源。 这种情况不太可能发生在由穴居动物和其他当地危害造成的个别堤坝决口事件中，因为现有的应急反应系统可以在几小时内对单个决口做出反应，并在几周内进行修复。另一方面，地震危险是一个非常大的威胁，因为三角洲内的许多岛屿可能同时被多个破坏所淹没。这种广泛的系统故障预计将导致长达28个月的时间，在此期间，从三角洲输送淡水将是不可能的。事实上，有些人质疑这样一系列的破坏是否会永久改变区域形态，从而需要确定替代水源，或者需要重新配置或重新安置加州经济/人口的主要部门。 地震震动对堤坝性能的影响是不确定的，因为对下面的泥炭质有机土壤的循环变形潜力还不清楚，迫切需要研究这些材料的性能。知识价值和范围：该奖项将支持现有土堤的全面测试（几何形状与堤坝非常相似，但目前不蓄水），以研究现实应力和边界条件下泥炭质有机地基土的原位变形潜力。试验条件和仪器的设计将用于测量可能导致临界干舷损失的变形机制，从而导致破坏。 这类数据对于开发更合理的分析工具来评估堤坝的地震易损性是必不可少的。现场测试将辅以广泛的实验室测试计划，以进一步研究关键的材料反应特性，如土壤强度损失和振动引起的体积减少。堤坝地震脆弱性的改进知识将广泛适用于这些土结构建立在有机土壤上的任何地方。 测试活动将与加州水资源部的工程师密切协调，以确定合适的地点。 从这个项目中获得的见解可能会从根本上改变三角洲地震风险评估和改造决策的方式。更广泛的影响：这项研究最重要的社会影响将是改善三角洲地区的地震风险评估，这反过来将导致更好的知情改造和/或建设决策，以及更有可能在地震震动期间和之后保持功能的供水系统。该奖项还将支持开发教育模块，利用NEES资源为更广泛的NEESinc教育，推广和培训（EOT）目标做出贡献。这些模块将讲授当前的输水系统，三角洲的堤坝网络，输水和堤坝网络之间的联系，这些堤坝的工程特性，堤坝的潜在地震破坏机制，以及对饮用水和灌溉用水的影响。这些单元将包括一份学习指南，其中载有关于在不同级别实施这些单元的建议（即，本科生和K-12）。该项目的数据将通过NEES数据库（http：//www.example.com）提供。www.nees.org