Past and Present Soft Ground NATM for Tunnel and Shaft Construction for the Washington, D.C. Metro

Synopsis:

The first application of soft ground NATM in the US was on Washington, DC Metro Section E5 Fort Totten Station and running tunnels.  Due to its success it was subsequently applied for tunneling under Rock Creek Cemetery and Section F6b, south of Congress heights station on the Outer Branch Route.  Tunneling for section E4b also called for the construction of a large NATM oval shaft that was used to stage tunnel construction.  In its final build-out it is configured as an emergency egress structure.  Application of the NATM and its successes laid the ground work for the method’s increased use on urban soft ground tunnels, recently the Beacon Hill station in Seattle.  NATM tunneling is currently being employed in a design-build framework for the extension of Washington’s Metro to Dulles International Airport.

Past and Present Soft Ground NATM for Tunnel and Shaft Construction for the Washington, D.C. Metro
2010 North American Tunneling Conference Proceedings
June 20-23, 2010
Portland, Oregon