GOALI: Performance of Deeep and Wide Excavations in Congested Urban Areas

美国和世界许多地区城市人口密度的增加要求我们在将民用基础设施扩展到地下环境的能力方面取得重大进展。地下空间的开发是持续和可持续的城市生活的关键。 在许多城市地区，地下空间利用面临的一个持续挑战是，在往往具有挑战性的土壤条件下，在建筑密集的环境中建造/开发该空间。旧金山弗朗西斯科市中心正在建设的跨湾交通中心（TTC，http：//transbaycenter.org/）是一个耗资20亿美元的公共工程项目，旨在用一个现代化的区域交通枢纽取代现有的跨湾终点站，该枢纽将连接11个交通系统，并将成为计划中的加州高速铁路从洛杉矶的终点站。 TTC的施工包括在相对较软的土壤中进行约200英尺宽、60英尺深、1500英尺长的明挖开挖。 该挖掘毗邻几座高层和低层建筑，包括旧金山弗朗西斯科最高的建筑之一。 TTC的建设必须对该地区的基础设施和经济活动造成最小的干扰。 这次挖掘在美国西海岸的规模是前所未有的，并将包括一个广泛的监测计划。这个项目的一个合适的类比是对一个跑马拉松的病人进行心脏直视手术。该研究项目是伊利诺伊大学厄巴纳-香槟分校，加州大学伯克利分校和奥雅纳之间的行业-大学合作伙伴关系，以利用这个独特的挖掘项目，以提高我们对非常广泛和长期挖掘的响应的理解，并开发合适的计算模型。 TTC挖掘超出了我们现有的经验数据库和验证模型。 该研究项目包括开发数值模型，执行补充实验室测试计划和安装旨在回答特定研究问题的补充现场仪器，利用项目岩土方面的现有投资。 现场仪表将包括跨批支撑上的应变计、伸长计以及在美国首次开发和使用的可冲洗压力计，以测量未加载粘土中的潜在负孔隙压力。 从实验室测试和现场监测程序的数据将被用于反分析，以产生新的土壤本构模型，并更新挖掘性能的预测。 分析也将进行，以更好地了解长期卸载对地下结构的地震反应的影响。 该研究项目将显著推进挖掘建模技术的最新发展。 这次挖掘的成功完成和获得的知识提供了宝贵的知识，可以应用于美国即将进行的大型地下基础设施投资，包括旧金山弗朗西斯科，洛杉矶，西雅图，纽约和迈阿密。 我们实现城市可持续生活的能力关键取决于在前所未有的挑战性环境中以前所未有的规模开发地下空间。 通过在该项目中获得的知识，我们将开发专业知识和技术工具，以自信地建造这些类型的结构，并将对城市环境的破坏降至最低。 我们将能够为决策者提供可靠的技术数据，以减轻传统上阻碍这些项目的社会忧虑和潜在阻力。 在许多教育活动中，我们与加州大学伯克利分校的少数民族参与联盟合作，让代表性不足的本科生参与这项研究项目。 从事该项目的学生将获得重大建设项目的宝贵现实经验，并将与研究人员和顾问互动。

The increase in urban population density in the US and many parts of the world requires major advances in our ability to extend civil infrastructure into the subsurface environment. Development of underground space is key to continued and sustainable urban living. A continuous challenge to underground space utilization in many urban areas is in constructing/developing that space in a heavily built environment in often challenging soil conditions. The Transbay Transit Center (TTC, http://transbaycenter.org/) under construction in downtown San Francisco is a $2 billion public works project designed to replace the existing Transbay terminal with a modern regional transit hub that will connect 11 transit systems and will be the terminus point for the planned California High Speed Rail from Los Angeles. The construction of the TTC includes an open cut excavation that is about 200 ft wide, 60 ft deep and over 1500 ft long in relatively soft soils. The excavation is adjacent to several high-rise and low-rise buildings including one of the tallest buildings in San Francisco. The TTC will have to be constructed with minimal disruption to infrastructure and economic activity in the area. The excavation is unprecedented in scale on the US West Coast, and will include an extensive monitoring program. A suitable analogy for this project is the equivalent of conducting open heart surgery on a patient running a marathon. This research project is an industry-university partnership between the University of Illinois at Urbana-Champaign, the University of California, Berkeley, and Arup to leverage this unique excavation project to enhance our understanding of the response of very wide and long excavations and to develop suitable computational models. The TTC excavations extend beyond our available empirical databases and validated models. The research project includes development of numerical models, performance of a supplementary laboratory testing program and installation of supplementary field instrumentation designed to answer specific research questions, leveraging current investments in the geotechnical aspects of the project. Field instrumentation will include strain gages on cross-lot bracing, extensometers and first development and use of flushable piezometers in the US to measure potential negative pore pressures in the unloaded clays. Data from the laboratory testing and field monitoring programs will be used in inverse analyses to generate new soil constitutive models and to update predictions of excavation performance. Analyses will also be conducted to better understand the impact of long term unloading on the seismic response of the underground structures. This research project will significantly advance state-of-the-art in excavation modeling techniques. The successful completion of this excavation and the acquired knowledge provides valuable knowledge that can be applied to large upcoming underground infrastructure investments in the US including San Francisco, Los Angeles, Seattle, New York and Miami. Our ability to achieve urban sustainable living is critically dependent on development of underground space in ever challenging environments at an unprecedented scale. Through knowledge gained on this project, we will develop the expertise and technical tools to confidently construct these types of structures with minimal disruption to the urban environment. We will be able to provide decision makers with the sound technical data that will alleviate societal apprehension and potential resistance that has traditionally impeded such projects. Among a number of educational activities, we have partnered with the Alliance for Minority Participation at UC Berkeley to engage underrepresented undergraduate students to assist with this research project. Students working on this project will gain invaluable real-world experience on a major construction project, and will interact with both researchers and consultants.