All elevated trackway spans through Tysons Corner will be of post-tension type construction. Not sure if the elevated trackway spans at station platform will also be of post-tension type construction as well. Past practice, at the Naylor Road station on F Route southern Green line would indicate otherwise as the trackway spans through that station were cast in place. Shorter spans over roads and streams will be of more conventional bridge construction. The casting plant for the fabrication of the precast concrete post-tension segments will located on Dulles Airport property off Pacific Boulevard east of the airport employee parking lot.
There will be total of three lifting gantries used to assemble the elevated spans along the Phase Phase I alignment. The lifting gantry is capable of advancing to the next span location without disassemble. It is also capable of moving laterally to allow the assemble of segments in the parallel spans.
The elevated trackways in the VA I-66 flyover spans will not be of post-tension type construction. A combination of Steel and precast concrete beams with a cast in place trackbed deck well be used there. The columns that will support fly over from the median of VA I-66 to the median of the Dulles Connector Road VA-267 will use the existing column piles that were built to accommodate the future branch back in the late 1970s when the road was originally built, see Washington Post graphic. The junction provision, under Haycock Road, (see first picture below) WMATA also built to accommodate the future branch will not be used, The junction will be located to the east under Great Falls Street.
As of 05 11 2010 progress on the NATM (New Austrian Tunneling Method) tunnels between Tyson Central 123 (Tysons Corner) and Tysons Central 7 (Greensboro) is, outbound track N2 830' inbound track N1 630'. Total length of each tunnel is roughly 2,400'. The reason why the progress distances are staggered is to prevent the possibility of subsidence in the overlaying soil. Finished tunnel linings will not be put in place until all of the excavation is completed.
No pictures along VA-7 Leesburg pike were taken as no work has started on any of the column piles. The contractors are still wrapping up utility relocation and preparation for temporary lane relocation still underway to accommodate the driving of the column piles.
Originally published 05 17 2010
Edited 05 02 2012
N Route Silver line flyover east of West Falls Church Station:
Post-tension lifting gantry #1.
In the pictures below the lifting gantry is positioned to assemble the inbound track N1 span.
|The near end is the sitting on the abutment.||This one gives you a sense of scale.|
Column construction in VA-267 Dulles Connector Road VA-123 Dolly Madison Boulevard interchange:
Column construction along Dolly Madison Boulevard, Tyson East (Mclean) station.
Column construction in VA- 495 Capitol Beltway VA-123 Dolly Madison Boulevard interchange:
Tysons Central 123 (Tysons Corner) station.
|Piling caps east end of Tysons Centeral 123 (Tysons Corner) station.||Piling caps east end of Tysons Centeral 123 (Tysons Corner) station.|
Cut and cover tunnel trenches in VA-7 Leesburg Pike VA-123 Dolly Madison Boulevard interchange:
Wiehle Avenue station:
|Wiehle Avenue station.||Wiehle Avenue station.||VA-267 Dulles Connector Road Dulles Access Road east of Wiehle Avenue.|
Pictures at picasaweb.google.com/cambronj 05-07-2010