Location

Arlington, Virginia

Session Start Date

8-11-2008

Session End Date

8-16-2008

Abstract

The Newseum consists of a 650,000 square-foot development that includes a six-level, 215,000 square-foot interactive museum of news. Also included is office space for the Newseum and Freedom Forum staff, a 9,000 square-foot conference center, more than 30,000 square feet of retail space and approximately 100 condominiums. The Newseum is located on Pennsylvania Avenue, between the U.S. Capital and the White House next to the Washington, D.C. mall and its museums and monuments. The building is supported on a mat foundation. The project is located just north of the Old Tiber Creek that was filled in the early 1800’s. Soft and compressible soils are present in the area that are prone to settlement from dewatering. These soils have also been associated with large movements of conventional H-pile and wood lagging excavation support systems and other problems in the past. Therefore, various “cut-off” walls were considered for excavation support that would not allow ground water levels around the building excavation to drop and would be less prone to soil erosion through wood lagging boards. Various cut-off walls were considered including a slurry wall, soil-mix wall, secant pile wall and Pile-in-Self-Hardening-Grout (PSHG) wall. A PSHG wall was selected for three sides of the excavation. The PSHG wall was constructed by inserting pre-fabricated panels consisting of steel H-piles and wood lagging into pre-excavated trenches using clamshell equipment normally used for slurry wall construction. A low strength self-hardening grout was used within the excavations to keep the sidewalls from caving, which hardened to strength of about 60 to 70 psi within a few days after installation of panels. The PSHG wall resulted in a relatively impermeable cutoff wall around three sides of the excavation. A secant pile wall was constructed at the east end of the excavation adjacent to the Canadian Embassy. The Canadian Embassy is founded on a mat foundation supported on relativity soft and compressible terrace age clay soils. A secant pile wall was selected adjacent to the Canadian Embassy to reduce the risk of settlement of the existing mat foundation. Ground water observation wells were monitored during construction to confirm that excessive ground water lowering below the Canadian Embassy mat did not occur. In addition, inclinometers and settlement points were monitored to measure movements of the Canadian Embassy, the secant pile wall, and PSHG wall. Both PSHG and secant pile walls were supported with tiebacks and both systems performed well within specified tolerances.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Sixth Conference

Publisher

Missouri University of Science and Technology

Publication Date

8-11-2008

Document Version

Final Version

Rights

© 2008 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Aug 11th, 12:00 AM Aug 16th, 12:00 AM

Excavation Support for the Newseum Development at 555 Pennsylvania Avenue in Washington DC, USA

Arlington, Virginia

The Newseum consists of a 650,000 square-foot development that includes a six-level, 215,000 square-foot interactive museum of news. Also included is office space for the Newseum and Freedom Forum staff, a 9,000 square-foot conference center, more than 30,000 square feet of retail space and approximately 100 condominiums. The Newseum is located on Pennsylvania Avenue, between the U.S. Capital and the White House next to the Washington, D.C. mall and its museums and monuments. The building is supported on a mat foundation. The project is located just north of the Old Tiber Creek that was filled in the early 1800’s. Soft and compressible soils are present in the area that are prone to settlement from dewatering. These soils have also been associated with large movements of conventional H-pile and wood lagging excavation support systems and other problems in the past. Therefore, various “cut-off” walls were considered for excavation support that would not allow ground water levels around the building excavation to drop and would be less prone to soil erosion through wood lagging boards. Various cut-off walls were considered including a slurry wall, soil-mix wall, secant pile wall and Pile-in-Self-Hardening-Grout (PSHG) wall. A PSHG wall was selected for three sides of the excavation. The PSHG wall was constructed by inserting pre-fabricated panels consisting of steel H-piles and wood lagging into pre-excavated trenches using clamshell equipment normally used for slurry wall construction. A low strength self-hardening grout was used within the excavations to keep the sidewalls from caving, which hardened to strength of about 60 to 70 psi within a few days after installation of panels. The PSHG wall resulted in a relatively impermeable cutoff wall around three sides of the excavation. A secant pile wall was constructed at the east end of the excavation adjacent to the Canadian Embassy. The Canadian Embassy is founded on a mat foundation supported on relativity soft and compressible terrace age clay soils. A secant pile wall was selected adjacent to the Canadian Embassy to reduce the risk of settlement of the existing mat foundation. Ground water observation wells were monitored during construction to confirm that excessive ground water lowering below the Canadian Embassy mat did not occur. In addition, inclinometers and settlement points were monitored to measure movements of the Canadian Embassy, the secant pile wall, and PSHG wall. Both PSHG and secant pile walls were supported with tiebacks and both systems performed well within specified tolerances.