Tunnel Design & Specialities

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.

The Heathrow Express Link provides a 15 minute high speed rail service between Paddington Station and Heathrow Airport. A 7.25 km spur running for the most part in tunnel provides the airport with underground stations at the Central Terminal area (Terminals 1, 2 & 3) and Terminal 4. Provision was also made for a link to the at this point proposed Terminal 5. The 5.5 km long tunnelled section will pass under the M4 motorway with the portal located to the north.