RAPID: Group Effects on Pile Downdrag Following Liquefaction

RAPID：液化后桩下拖力的群效应

• 批准号: 2006323
• 负责人: Richard Coffman
• 金额: $ 7.5万
• 依托单位: University of Arkansas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-12-01 至 2021-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2006323&HistoricalAwards=false
• 关键词: RAPID; Group; Effects; Pile; Downdrag

Several of the earthquakes that occurred during the 1811-1812 New Madrid earthquake sequence were identified by the United States Geological Survey as being the largest earthquakes East of the Rocky Mountains and within the top 20 of the largest domestic earthquakes United States history. The seismic waves from these earthquakes propagated for a great distance because of the competency of the surrounding bedrock, and because the earthquakes occurred in the middle of the continental plate. Soil liquefaction, where soil below the water table temporarily becomes a viscous fluid following shaking, was observed to occur during the New Madrid earthquakes. Liquefaction results in a loss of strength in the soil that serves as the bearing material for most infrastructure. If the same size earthquake as the 1811-1812 sequence were to occur today, the United States Federal Emergency Management Agency warns that the earthquake could result in the highest economic losses due to a natural disaster in the United States. Because the areas near the earthquake are now densely populated (St. Louis, Missouri, and Memphis, Tennessee) additional understanding of behavior of civil infrastructure when exposed earthquake induced liquefaction is needed to prevent loses. To remedy this lack of understanding, small explosive charges will be used to produce liquefaction under full-scale conditions and measurements will be made of the foundation settlement and the downward friction force on the foundations. Tests will be performed on two pile groups a site in Arkansas. Primary support will be provided by Nucor Yamata Steel Corperation; however, supplemental funding from NSF will significantly expand the scope of the project. This Rapid Response Research (RAPID) grant will provide that supplemental funding. The results from these tests will allow engineers to evaluate the accuracy of existing design procedures and develop modifications to produce better agreement with measured behavior. Improved design procedures will allow engineers to design safer yet cost-effective foundation solutions that will remain stable during earthquakes. Limitations of the previous study at the Turrell Arkansas Test Site will be overcome by 1) testing groups of piles instead of individual piles, 2) leaving the deadload on the foundations for a longer period of time prior to blasting to allow the neutral plane to develop, and 3) leaving the deadload on the foundations for a longer period of time after blasting to allow the neutral plane to redevelop.To improve our understanding of liquefaction-induced downdrag/dragload on deep foundations, blast induced liquefaction tests will be performed on two different pile groups (steel pipe group, H-pile group) at a site in Arkansas. The objective is to measure negative skin friction and downdrag induced settlement. With the inclusion of a static load placed on top of the pile groups, the results from these tests will allow researchers to evaluate the accuracy of existing design recommendations and develop modifications to produce better agreement with measured response. Because deep foundations are a common approach for supporting structures in liquefiable sands, reliable design approaches are critical to provide cost-effective foundations that are safe in future earthquakes. The results obtained from this project will be used to mitigate liquefaction induced damage at other earthquake prone sites with a similar geologic profile.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

美国地质调查局确定了1811 - 1812年新马德里地震序列期间发生的几场地震是落基山脉以东的最大地震，在美国最大的国内地震历史上最大的20次地震。 由于周围的基岩的能力，这些地震的地震波在很大程度上繁殖，并且由于地震发生在大陆板的中间。 在新的马德里地震期间，观察到在摇动后地下水位下方的土壤暂时变成粘性的液体。液化导致土壤中的强度损失，这是大多数基础设施的轴承材料。如果今天发生与1811-1812序列相同的地震，美国联邦紧急事务管理局警告说，由于自然灾害，地震可能导致最高的经济损失。 由于地震附近的区域现在人口稠密（圣路易斯，密苏里州和田纳西州孟菲斯）时，需要在暴露地震引起的液化时对民用基础设施的行为进行更多了解以防止损失。 为了补救这种缺乏理解，将使用小的爆炸费来在全尺度条件下产生液化，并将对基础定居和基础的下降摩擦力进行测量。测试将在阿肯色州的两个桩组的一个地点上进行。主要支撑将由Yamata Steel Corperation提供；但是，NSF的补充资金将大大扩大项目的范围。这项快速响应研究（快速）将提供补充资金。这些测试的结果将使工程师能够评估现有设计程序的准确性，并开发修改以更好地与测量行为达成一致性。改进的设计程序将使工程师可以设计更安全但具有成本效益的基础解决方案，这些解决方案将在地震期间保持稳定。先前研究在阿肯色州Turrell测试地点的局限，和3）在爆破后将其留在基础上较长的时间内，以允许中性平面重新开发。为了提高我们对液化引起的降水/拖动的理解，在深基础上，将在两个上进行爆炸诱导的液化测试在阿肯色州的一个地点，不同的桩组（钢管组，H-PILE组）。目的是测量皮肤摩擦和下垂引起的沉降。随着将静态负载置于堆组的顶部，这些测试的结果将使研究人员能够评估现有设计建议的准确性，并开发修改以与测量的响应产生更好的一致性。由于深层基础是在液化砂中支撑结构的常见方法，因此可靠的设计方法对于提供在未来地震中安全的成本效益基础至关重要。 从该项目获得的结果将用于减轻其他地震易于地地质概况的液化造成的损害。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力优点和更广泛的影响来评估的审查标准，因此被认为值得支持。 。