RAPID/Collaborative Research: Spatial Variability of Small-Strain Stiffness, Go, and Effects on Ground Movements Related to Geotechnical Construction in Urban Areas

快速/协作研究：小应变刚度、Go 的空间变化以及对城市地区岩土工程施工相关地面运动的影响

• 批准号: 1841576
• 负责人: Khiem Tran
• 金额: $ 2.7万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1841576&HistoricalAwards=false
• 关键词: RAPID; Collaborative; Research; Spatial; Variability

Increased dense urbanization and traffic congestion in the US is prompting a significant demand for underground space. Underground construction provides sustainable development benefits in terms of creating mass transit and commercial space in areas with existing infrastructure, the ability to capture emissions, and the opportunity to preserve green space by relocating transportation systems and other structures underground. However, development of underground space may result in damage to adjacent infrastructure. Furthermore, planning and constructing underground space is a lengthy process that requires large budgets, and most underground construction are public, taxpayer-funded projects. Efficiencies that can be developed in design and construction of underground space will have a large financial benefit to the US. This Grants for Rapid Response Research (RAPID) project will develop tools that will advance the state-of-art and practice in the underground construction industry so that underground space can be created in urban areas in such a way that the process will have minimal impact on adjacent structures and utilities. Recent NSF sponsored research has resulted in advances in techniques to predict, monitor, and control ground movements during excavation. These efforts have shown that small-strain shear stiffness of soil, Go, and its variation with strain is a key ingredient in a model used to predict ground movements. Engineers need to have accurate predictions of ground motion caused by excavations because excessive movements (often and inch or less) can cause damage to adjacent infrastructure and structures. An accurate estimate of movement will allow engineers to adjust their design to limit the movement to an acceptable level. Natural soils are heterogeneous and Go values vary laterally and with depth around the plan area of typical urban excavations. This project will determine the spatial variations of Go around a large excavation in Seattle, WA, specifically the Washington State Convention Center Addition (WSCCA), and quantify the effects of the variations on measured and predicted ground movements that arise during excavation. The project is a collaboration between Northwestern University, the University of Texas at Austin, the University of Florida and GeoEngineers, Inc. Collaboration, at no cost to the project, with GeoEngineers, a leading geotechnical consulting firm in the country and the geotechnical engineers of record for the WSCCA project, ensures that results will have an immediate impact in the underground construction community. The WSCCA excavation provides a number of unique opportunities. A large portion of the site is green space, and as such, the initial Go variation in most of the site will mostly be unaffected by previous construction activities. Therefore, when Go is evaluated after excavation, a direct measure of the change in the soil properties will be available. These measurements are rarely, if ever, performed. The project team will obtain spatially dependent Go values prior to start of construction using NHERI@UTexas field equipment and SASW arrays; analyze the seismic data via advanced 3-D full waveform tomography to develop a 3-D map of Go; conduct detailed experimental programs using both advanced triaxial and combined dynamic torsional resonant column and cyclic torsional shear devices on thin-wall tube and block samples; develop soil parameters for an advanced constitutive model that includes small-strain stiffness using optimization techniques based on the laboratory data and the field measurements collected during excavation; collect and record field performance and relate it to construction activities; and simulate the excavation process using the finite element method. While addressing ground deformations specifically associated with deep excavations, the project results are applicable to any geotechnical construction activity. There is very little detailed information concerning the stress-strain-strength characteristics of the glacially consolidated soils in the Seattle area, and information developed as part of this project will be useful for any large project in the vicinity. The project team will disseminate its results to the scientific and professional communities by means of journal publications and conference presentations. The interactions among GeoEngineers, Inc. professionals, NU, UT and UF participants via project interaction and seminars automatically will foster the rapid technology transfer of these advances. A NHERI@UTexas user workshop also will be held during the field study.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.

美国日益密集的城市化和交通拥堵促使人们对地下空间产生了巨大的需求。 地下建筑提供了可持续发展的好处，在现有基础设施的地区创造公共交通和商业空间，捕获排放的能力，以及通过将交通系统和其他结构重新安置在地下来保护绿色空间的机会。 然而，地下空间的开发可能会对邻近的基础设施造成损害。 此外，规划和建设地下空间是一个漫长的过程，需要大量的预算，大多数地下建筑是公共的，纳税人资助的项目。 在地下空间的设计和建设中可以开发的效应将对美国产生巨大的经济效益。 这个快速反应研究（RAPID）项目的赠款将开发工具，以推进地下建筑行业的最新技术和实践，以便在城市地区创造地下空间，从而使该过程对相邻结构和公用设施的影响最小。 最近NSF赞助的研究导致了挖掘过程中预测、监测和控制地面运动技术的进步。 这些努力表明，土壤的小应变剪切刚度Go及其随应变的变化是用于预测地面运动的模型中的关键因素。 工程师需要对挖掘引起的地面运动进行准确的预测，因为过度的运动（通常是一英寸或更小）可能会对邻近的基础设施和结构造成损坏。 对运动的准确估计将允许工程师调整他们的设计，以将运动限制在可接受的水平。 天然土壤是异质的，Go值横向变化，并随着典型城市开挖的平面区域周围的深度变化。 本项目将确定华盛顿州西雅图的大型挖掘工程（特别是华盛顿州会议中心扩建工程（WSCCA））周围的空间变化，并量化这些变化对挖掘过程中出现的测量和预测地面运动的影响。 该项目是西北大学、德克萨斯大学奥斯汀分校、佛罗里达大学和地球工程公司之间的合作项目。 该项目与国内领先的岩土工程咨询公司GeoEngineers以及WSCCA项目的岩土工程师进行了免费合作，确保结果将对地下建筑界产生直接影响。WSCCA的发掘提供了许多独特的机会。 场地的很大一部分是绿色空间，因此，场地大部分区域中的初始Go变化将大部分不受先前施工活动的影响。 因此，当在开挖后对Go进行评估时，可以直接测量土壤性质的变化。 这些测量很少进行，如果有的话。 项目小组将在开始施工前使用NHERI@UTexas现场设备和SASW阵列获得空间相关的Go值;通过先进的三维全波形层析成像分析地震数据，以绘制Go的三维图;在薄壁管和块样品上使用先进的三轴和组合动态扭转共振柱和循环扭转剪切装置进行详细的实验方案;根据挖掘期间收集的实验室数据和实地测量结果，利用优化技术，为包括小应变刚度在内的高级本构模型制定土壤参数;收集和记录实地表现，并将其与施工活动联系起来;利用有限元法模拟挖掘过程。 在解决与深开挖特别相关的地面变形时，项目结果适用于任何岩土工程施工活动。 关于西雅图地区冰川固结土壤的应力-应变-强度特性的详细资料很少，作为本项目一部分开发的资料将对附近的任何大型项目有用。 项目小组将通过期刊出版物和会议介绍向科学界和专业界传播其成果。 GeoEngineers，Inc.专业人士，NU，UT和UF参与者通过项目互动和研讨会自动将促进这些进步的快速技术转让。 该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。