The Washington Metropolitan Area Transit Authority (WMATA), which pioneered the U.S. use of the New Austrian Tunneling Method (NATM) in a rapid transit segment in 1986, is now using the NATM for the first time in soft ground in a project in Fort Totten. The project is progressing at half the expected pace, but is expected to pick up as managers and workers become accustomed to the technique. NATM is slower in soft soil (target is 7 ft a day) than in rock (it advanced 20 to 30 ft per day). In soft earth, only 3 ft can be opened up at a time and then the earth has to be supported as work moves ahead. Excavation is controlled by spraying with shotcrete, installing wire fabric, and erecting lattice-girder ribs on 3 ft centers. The tunnels will then be waterproofed. An 80-ft ventilation shaft with an elliptical cross section about 81 ft across was driven in. This is an extensive R&D project with extensive documentation to show that it is a safe technique.

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    McGraw-Hill, Incorporated

    330 West 42nd Street
    New York, NY  United States  10036
  • Publication Date: 0

Media Info

  • Pagination: p. 51-52
  • Serial:
    • ENR
    • Volume: 223
    • Issue Number: 16
    • Publisher: McGraw-Hill, Incorporated
    • ISSN: 0891-9526

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Filing Info

  • Accession Number: 00489503
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Nov 30 1989 12:00AM