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Tunnel Design & Specialities

Washington Dulles Airport Pedestrian Walkback Tunnel

Service Performed
Final design including FEM structural calculations.
Commencement - Services
February 01, 1998
Completion - Services
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
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.

Activity
Categories
Final cost
$13,000,000
Service areas
Construction methods
Max Overburden
Min:10 Max:20
Max Excavation Area (m2)
Min:1200 Max:1200
Tunnel length
Min:770 Max:770
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
Project number
207D
Final cost
$13 million USD

Heathrow Express Rail Link

Service Performed
Tender design, detailed design and construction supervision.
Commencement - Services
April 01, 1990
Completion - Services
December 27, 1992
Location
Nelson Road
London
TW6 2GW
United Kingdom
Technical data

Railway link between Heathrow Airport and Paddington Station 2 underground stations: (Central Terminal and Terminal 4). Trial station tunnel with three different excavation and support sequences; lenght: 100 m, diameter: 8 m approx.

Geology description

Soft ground, terrace gravels overlying London Clay.

Geology types
Description

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.

Activity
Final cost
$2,200,000
Service areas
Tunnel Design & Specialities
Removal of temporary side wall
Shotcrete lining completed
Finished adit
Subway entry at surface
Lattice girder and wire mesh installed at invert
Excavation of bench completed
Excavation of the side drift
Invert,installed lattice girder and wire mesh
Installed pressure cells
Installation of L.G. in top heading of side drift
Proposed Excavation Sequences
Instrumentation Scheme
Finite-Element Calculation
Excavation Sequence Type 1
Excavation Sequence Type 2
Excavation Sequence Type 3
Completed Trial Tunnel
Finished Platform Heathrow Central Terminal
Concourse Tunnel
Completed Escalator Shaft
Project number
172D
Final cost
£2.2 million GBP

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