| NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
| Recipient: |
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| Initial Amendment Date: | July 31, 2018 |
| Latest Amendment Date: | July 31, 2018 |
| Award Number: | 1841584 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Joy Pauschke
jpauschk@nsf.gov (703)292-7024 CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
| Start Date: | August 1, 2018 |
| End Date: | July 31, 2020 (Estimated) |
| Total Intended Award Amount: | $99,999.00 |
| Total Awarded Amount to Date: | $99,999.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
633 CLARK ST EVANSTON IL US 60208-0001 (312)503-7955 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
2145 Sheridan Rd Evanston IL US 60208-3109 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | ECI-Engineering for Civil Infr |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
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.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
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, the ability to capture emissions, and the opportunity to preserve green space by relocating transportation systems and other structures underground.
Development of underground space can, however, result in damage to adjacent infrastructure. Recent research has resulted in advances in techniques to predict, monitor, and control ground movements during excavation. One theoretical aspect of these efforts has shown that small-strain shear stiffness, Go, and its variation with strain is a key ingredient in any constitutive model used to predict the relatively small ground movements required to preclude damage to adjacent infrastructure and structures in urban areas. Natural soil sites are heterogeneous and Go values vary laterally and with depth around the plan area of typical urban excavations. The purpose of this research was to obtain, using the Natural Hazards Engineering Research Infrastructure (NHERI)@UTexas field equipment, spatially dependent shear wave velocities values around the excavation for the Washington State Convention Center (WSCC) in Seattle, WA. Both Spectral Analyses of Surface Waves (SASW) and 3-D tomography were conducted to determine the shear wave velocities. Numerical analyses were conducted and wall movement data were collected to evaluate the impact of Go based on these data on the resulting ground movements that arose during the excavation process. The project was a collaborative effort between Northwestern University (NU), the University of Texas at Austin (UT), the University of Florida (UF) and GeoEngineers, Inc. of Seattle.
The research defined small strain stiffness over a relatively large volume of ground which was subsequently stressed by excavation. The 3D tomography results provided more detail than the SASW results in defining the stiffness of the soils encountered. The observed wall deformations adjacent to the tested section recorded during excavation quantified the effects of natural variability in this geologic setting on numerically-computed ground movements. Constitutive model parameters were developed that bounded the observed variability in the Go field results. Use of in situ measurements of shear wave velocity were shown to be indispensable to define directly important portions of constitutive soil responses, including both the magnitude and expected variation in shear stiffness for these conditions.
The societal and educational impacts of the research are broad, because its results impact the basic science needed for developing sustainable geotechnical designs in urban areas. The NHERI equipment has been mainly applied to earthquake engineering applications and results obtained by it, and other similar equipment, have now been shown to be applicable to any project where structures are well-designed and under working stress conditions.
Last Modified: 07/21/2020
Modified by: Richard J Finno
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