FOUNDATION UNDERPINNING FOR STRUCTURES OVER SUBWAY EXCAVATION

To protect structures from settling due to the excavation for the Washington, D.C., subway, it was necessary to underpin their foundations. For the soil and construction conditions of this project, the influence zone for major historic and public buildings was defined as the area above a line rising from each side fo the excavation at a slope of 1:1 from a point 2 ft (0.61 m) below the edge of the base of the subway excavation. Building foundation bearing areas above the influence zone were underpinned to deliver the foundation load below this sloping line. Work on two of the 36-year-old Superior Court Building of reinforced concrete and/or structural steel in Judiciary Square is described in this article. In general, the underpinning involved transferring those column loads and building wall loads, which are outside the subway excavation limits, but within the influence zone, to a pile foundation. Construction directly over the subway excavation was transferred onto prestressed concrete beams which spanned the excavation and rested on new pile foundations constructed on each side of the excavation. All foundations within the influence zone had to be temporarily supported on "pickup" beams while they were being undermined for pile installation, so as to avoid foundation movement.

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Filing Info

  • Accession Number: 00127134
  • Record Type: Publication
  • Report/Paper Numbers: 72-28
  • Files: TRIS
  • Created Date: Jan 14 1982 12:00AM