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Washington Dulles Airport Pedestrian Walkback Tunnel

Final design including FEM structural calculations.
Estimated cost: Commencement:
February 01, 1998
Completion date:
December 01, 2001
45045 Aviation Drive
Dulles, VA 20166-7528
United States
Technical data:

Pedestrian Walkback tunnel, accommodating two moving and one central fixed walkways, 770 ft long, Section of 41 ft x 27 ft. A Mechanical Room with a 37 ft long x 32 ft. span . Tunnel passing 15 ft beneath the main airport taxiways.

Geology description:

Residual soils, decomposed rock and siltstone bedrock.

Geology types:
Bid cost: Final cost:
$13 million USD
Service areas:
Construction methods:
Min:10 Max:20
Excavation area:
Min:1200 Max:1200
Tunnel length:
Min:770 Max:770

An extensive underground people-mover train system and a fixed walkway tunnel between terminals are central to a multi-phased mega program of modernization and expansion for the Washington Dulles International Airport. The pedestrian walkback tunnel, a part of the expansion plan, crosses below two airport taxilanes and will connect the Main Terminal with Mid-Field Concourse B. The tunnel was designed as a multiple-drift NATM excavation, whereby cover beneath the taxilanes was less than a tunnel diameter at only 4.5 m. Excavation was therefore designed as a very controlled sequence with top heading excavation further divided into two side drifts.

Walkback tunnel cross section
Access shaft and portal under taxilane
The new tunnel in relation to the airport taxiways
Excavation of Access Shaft
View from Portal to Main Terminal Building
Excavation of Connector Shaft at Junction to Walkback Tunnel
Roadheader entering the Tunnel
Access Tunnel Walkback Tunnel Junction
Access Tunnel Walkback Tunnel Junction
Walkback Tunnel Shotcrete Canopy
Flexible Membrane Waterproofing System applied to Tunnel Invert
Installation of Waterproofing System in Connector Shaft
Fixing of Waterproofing Membrane
Completed Shotcrete Final Lining
Shotcrete canopy, girder erection
Shotcrete Arch - South
Shotcrete Arch - South
Hanging Steel Mesh
Hanging Steel Mesh
Hanging Steel Mesh
Girder completly installed
Shotcrete canopy completed