History and Recent Developments in Soft Ground NATM Tunneling for the Washington, D.C. Metro

Synopsis:

The first application of soft ground NATM in the US was on Washington, DC Metro’s Section E5 Fort Totten Station and tunnels.  Due to its success it was subsequently applied to the tunneling under Rock Creek cemetery, Section E4b, and a few years later on Section F6b on the Outer Branch Avenue south of Congress Heights Station.  The application and its successes laid the ground work for the method’s increased use on many urban soft ground tunnels in US cities.  Soft ground NATM tunneling will be used again for the extension of Washington’s Metro to Washington Dulles International Airport.

In this paper the authors provide detailed case history summaries and describe developments and refinements of the NATM in Washington ranging from technical to contractual to new risk management aspects.  Many innovations that led to the method’s refinements and its widespread use in the US were pioneered on the Washington, D.C. Metropolitan Area Transit Authority (WMATA) Metro system and during its continued use on Metro, namely for the Dulles Corridor Metrorail project at Tysons Corner, Virginia, where soft ground NATM construction will start in mid 2009.

History and Recent Developments in Soft Ground NATM Tunneling for the Washington, DC Metro
2009 World Tunnel Congress and 35th ITA General Assembly Proceedings
Budapest, Hungary
May 23-28, 2009