Washington Metro hosted a European professional group interested in rapid transit construction with particular attention on tunneling. Ultimately the 103-mile system will have 87 stations. Problems of planning and funding a regional system in several political jurisdictions complicated also with federal funding are initially described. This portion of the report is followed by detailed descriptions of two tunneling projects inspected by the group. Soft Ground TBM Link describes part of the Yellow/Green Line construction through water-bearing sand and gravel where settlement of old buildings and sub-surface utilities was also a problem. The contractor initially submitted a Value Engineering Cost Proposal which can propose alternatives to contract specifications that show the job can be done safely and quickly but more economically. A full-face tunnel boring machine was utilized without resorting to compressed air and dewatering. The tunnel was lined with reinforced concrete segments. NATM a winner for Wheaton describes use of the New Austrian Tunneling Method by an Austrian contractor to build one end of the Red Line. In NATM the rock with its cover of immediate shotcrete is induced to become self-supporting. The waterproofing is also much simplified. Rockbolting supplements the immediate support and ultimately a reinforced concrete lining is placed inside a waterproof membrane. Excavation involves drilling and blasting. Tunneling on the 2500-m twin tunnels started in May 1984 and is to be completed in 1987, including one subway station.

  • Availability:
  • Corporate Authors:

    Morgan-Grampian (Construction Press) Limited

    Morgan-Grampian House, 30 Calderwood Street
    London SE18 6QH,   England 
  • Publication Date: 1985-6

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 23-30
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00399813
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 30 1985 12:00AM