Washington Dulles Airport Pedestrian Walkback Tunnel

Owner:	Metropolitan Washington Airports Authority
Client:	Kaiser Engineers / Earthtech
Service:	Final design including FEM structural calculations.
Estimated cost:		Commencement:	February 01, 1998	Completion date:	December 01, 2001
Location:	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:	Mixed face
Activity:	Design
Categories:	Airport Tunnel
Bid cost:		Final cost:	$13 million USD
Service areas:	Site Supervision & CM, QA/QC, Tunnel Design & Specialities, Waterproofing & Water Control
Construction methods:	NATM
Overburden:	Min:10 Max:20
Excavation area:	Min:1200 Max:1200
Tunnel length:	Min:770 Max:770

Description

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