Highway construction behind TBM Bertha
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16 Nov 2016: As TBM Bertha continues to progress stead and careful excavation of the Alaskan Way SR99 viaduct replacement tunnel in Seattle, construction of the internal structures for the double-deck highway within the 9,000ft long x 17.4m o.d. tunnel also progress as a rolling program behind. Chris Dixon, Project Manager for construction JV Seattle Tunnel Partners (STP), explains the process of building the internal structures while maintaining services at all times through to the advancing TBM.

References
Half-way milestone for TBM Bertha - TunnelTalk, October 2016
Internal structures of the Eurasia double-deck highway tunnel in Istanbul - TunnelTalk, September 2015
Best value proposal for Alaskan Way - TunnelTalk, December 2010

Snapshot

Highway construction behind TBM Bertha

Sterling Noren reporting for TunnelTalk from Seattle
Project: Alaskan Way Viaduct replacement tunnel, Seattle
Contractor: Seattle Tunnel Partners Dragados - Tutor Perini JV
Client: Washington State Department of Transportation
Project scope: World's largest single-tube, double-deck highway tunnel
Tunnel design: Mega-EPBM, 17.48m o.d., to drive the 2.7km highway tunnel under the streets of downtown Seattle
Internal structures: Two road decks, side walls, and equipment rooms
Internal structure progress: In-situ concrete structures cast in 54ft sections
Upper road deck: Cast in place
Lower road deck: Precast panels installed once TBM tunneling is complete and all TBM service lines are removed
Revised schedule: TBM excavation completed by early 2017
Highway tunnel to open by end of 2018