Tunnel Tysons Corner

twin tube Metro tunnel

Client

Metropolitan Washington Airport Authority (MWAA)
USA

Contractor

Dulles Transit Partners LLC., Vienna, VA, USA
Know-How-Contractor:
Beton- und Monierbau USA, Inc. a 100% subsidiary of BeMo Tunnelling GmbH
Specialised support for NATM soft ground tunnelling

Project location

Dulles Corridor Metrorail Project (DCMP), Tyson Corner
Virginia
USA

Start of construction

2009

End of construction

2011

Project total value

4.5 million €

Geology

Costal plane and Piedmont sediments under shallow overburden

Technical Data

• Twin tube Metro tunnel (as part of an 11 miles Metro extension towards Dulles airport)
• Total length of tunnel: 2 x 1600 ft (2 x 500 m)
• Shallow overburden: 10 to 40 ft (3 to 12 m) only, with a main traffic road on top
• Cross-Section (min): 390 SF (36.2 m²)
• This could be done only by applying a forepoling support (steel pipes for the canopy – pipe arch canopy), which created a specific sawtooth shape to the initial liner. The length of the pipes was 18 m and the sawtooth had 12 m.
• The general excavation and support sequence followed the principles of SEM/NATM
• The sawtooth was filled partially with shotcrete
• Waterproofing: 2 mm PVC membrane
• 40 blocks of the final liner were reinforced

Further project related information

• Tunnel excavation undercrossing roads, utilities and hotels close by
• Water-table approx. beyond springline
• Intensive ground monitoring