Location

Chicago, Illinois

Session Start Date

4-29-2013

Session End Date

5-4-2013

Abstract

In the observational method, gaps in the available information are filled by observations. Such observations were invaluable during the construction of a 54-story building with an 8-story underground parking deck in Charlotte, North Carolina, which required an excavation nearly 100-feet deep into rock. Cracks appeared in an adjacent brick office building by the time the north side of the excavation had reached a depth of about 40 feet. Blast-induced settlement was initially suspected. As excavation continued, some soilfilled weathered joints, seams, and fractures in the rock sidewalls were observed, and displacement of the cracks increased. Inclinometer casings were installed along the street bordering the north sidewall. After increasing deformation, the casings began to shear at a depth of about 47 feet. A clay-filled seam dipping into the excavation at an angle of 10 to 15 degrees was discovered in the north sidewall. A row of grouted No. 18 bars was installed in drill holes angled across the clay seam. After analysis of a sliding block model revealed the need for additional capacity, a row of shear pins was installed in the street behind the north sidewall. No further movement was observed.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Seventh Conference

Publisher

Missouri University of Science and Technology

Publication Date

4-29-2013

Document Version

Final Version

Rights

© 2013 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 29th, 12:00 AM May 4th, 12:00 AM

Observations Save the Day at the Wachovia Cultural Center Excavation

Chicago, Illinois

In the observational method, gaps in the available information are filled by observations. Such observations were invaluable during the construction of a 54-story building with an 8-story underground parking deck in Charlotte, North Carolina, which required an excavation nearly 100-feet deep into rock. Cracks appeared in an adjacent brick office building by the time the north side of the excavation had reached a depth of about 40 feet. Blast-induced settlement was initially suspected. As excavation continued, some soilfilled weathered joints, seams, and fractures in the rock sidewalls were observed, and displacement of the cracks increased. Inclinometer casings were installed along the street bordering the north sidewall. After increasing deformation, the casings began to shear at a depth of about 47 feet. A clay-filled seam dipping into the excavation at an angle of 10 to 15 degrees was discovered in the north sidewall. A row of grouted No. 18 bars was installed in drill holes angled across the clay seam. After analysis of a sliding block model revealed the need for additional capacity, a row of shear pins was installed in the street behind the north sidewall. No further movement was observed.