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WMATA Section F6b, Branch Route

NATM Design
Estimated cost: Commencement:
January 10, 1996
Completion date:
December 30, 1997
Washington, DC
United States
Technical data:

Subway running tunnels 2 x 1,400 ft (427m) long, 20' wide x 21' high with a section of 342 sqft (32m²). Tunnels included a section with chemical grouted arch pre-support in P2 sands installed using directional drilling methods. "Closed Bag" PVC waterproofing using sectioning system. Unreinforced concrete final lining.

Geology description:

Tunneling through compact to very compact fine to medium sand of the P2 stratum (below the ground-water table) and stiff to hard plastic to silty clay of the P1 stratum.

Geology types:
Bid cost: Final cost:
Service areas:
Shotcrete Application in Top Heading
Portals of the NATM Running Tunnels
Top Heading Excavation
Initial Lining of NATM Type Cross Section
Initial Lining of circular Cross Section
Waterproofing at Cut & Cover Section
Waterproofing at Escalators
Waterproofing Installation at Portals
Installation of Waterproofing Membrane
Welding of PVC Membrane
Finished Waterproofing Membrane
Installation of Reinforcement
Completed Concrete Final Lining
Finished Tunnel
Waterproofing installed
Shotcreting the top heading