RAPID: Adaptive Management of Geotechnical Construction in Urban Areas

Northwestern University, Evanston IL

Investigators

Abstract

Increased dense urbanization and traffic congestion in the US and many parts of the world are prompting a significant demand for underground space to make emerging mega-cities livable by lowering pollution and energy consumption. Underground construction provides sustainable development benefits in terms of creating mass transit and commercial space in areas with existing infrastructure, with the ability to capture emissions, and the opportunity to preserve green space by relocating transportation systems and other structures underground. However, planning and construction of underground space is a lengthy process that requires large budgets (over $100 billion annually in the U.S.). Cost and schedule delays are common (e.g., Boston Big Dig from initial estimate of $2 billion to over $13 billion). Most of underground construction is public, taxpayer-funded projects. Efficiencies that can be developed in design and construction of underground space thus will have a large financial benefit to the US. One such development is an adaptive management technique that provides a means to incorporate recent advances in sensor development, information technology, and numerical analyses to predict, monitor, and control ground movements during excavation. The purpose of this research is to employ for the first time adaptive management techniques for geotechnical construction to provide real time updates of performance predictions, in this case during the 50 foot deep excavation for a multi-story building in Chicago. The 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, thereby minimizing construction costs and eliminating expensive construction claims and lawsuits. While this project focuses on adaptive management of deep excavations, its results are directly applicable to any geotechnical construction activity. Industrial collaboration with Hayward Baker, Inc., the excavation support contractor for the project and a worldwide leader in geotechnical specialty construction, will ensure that results will have immediate impact in the underground construction industry. This research builds upon the results of several of NSF-supported projects in which optimization techniques were developed, automated monitoring technologies were employed, full-scale field performance was quantified in detail, sophisticated models of soil behavior were employed, and parameter identification techniques were quantified at deep excavation sites. The test bed for this research is the excavation for the Simpson Querrey Biomedical Research Center building. The work will be conducted by Northwestern University in collaboration with Hayward Baker, Inc., the excavation support subcontractor for the project. The Principal Investigator conducted extensive research during and after construction of the adjacent Lurie Research Center which included a 40 ft deep excavation. At no cost to the research, Hayward Baker will install and maintain an automated monitoring system which will include MEMS-based shape arrays to measure lateral movements, robotic total stations to measure support system and adjacent building movements. Northwestern researchers will develop 2D and 3D finite element models of the excavation, based on constitutive models that account for small strain nonlinearity behavior of soils, implement an interface between the website, develop an analyses platform to allow automatic updates of performance predictions based on the finite element model, and deploy students as field personnel to record the detailed construction activities which will assure that the proper conditions have been considered in the update of the field performance. The research addresses fundamental issues regarding stress-strain behavior of natural clays at very small strain levels, and the relationships between detailed soil and structural responses due to construction activities. The tools will include integrated analyses and information platforms to facilitate communication among engineers, contractors, owners and the public, and will permit updated predictions of performance in near real time.