Seattle prepares for mega-TBM assembly 02 May 2013
TunnelTalk reporting
All is now ready in the job site launch pit to start assembly of the 17.48m diameter EPBM ready for its 2.73km drive beneath the streets of Seattle. Construction of a double-decked highway replacement of the SR-99 Alaskan Way elevated viaduct across the waterfront of the city will allow for its demolition.
Launch pit readied for TBM assembly

Launch pit readied for TBM assembly

Components of the world's largest ever TBM arrived in Seattle from Japan at the end of March and are now sorted in sequence ready for lowering into the launch pit for assembly. Designed and manufactured by Hitachi Zosen, the enormous TBM was assembled for factory testing in December before being shipped to Seattle in March.
With the arrival dock and storage facility for the components lying close to the southern end of the project's tunnel alignment, close to the foreshore, assembly of the TBM has begun. TunnelTalk video journalist Sterling Noren is on the beat in Seattle for the duration of the project. At a special media event he was on site to record operations and gather news from senior managers with STP, the Seattle Tunnel Partners contracted to complete the design-built highway project, and WSDOT, the Washington State Department of Transportation and owner of the existing viaduct and the new infrastructure.

TunnelTalk catches the action in Seattle

As with all major projects there is a long list of suppliers, subcontractors and materials providers who contribute to the whole. For the mega machine in Seattle, vital elements of the whole are the moulds supplied to cast the massive segments for the precast concrete segmental lining, and the erector on the machine to lift them into the ring build. Both of these elements are supplied to the project by CBE.
The French company has supplied 40 moulds for four rings sets, with each ring comprising seven standard segments, two key and one counter-key stones. Each ring segment is 2133mm wide and 610mm thick. The ring dimensions necessary to cope with the specific needs of the project were investigated by engineers at CBE, and by the contractor, STP. An outside diameter for the segmental lining of more than 16m was necessary, and a thickness of more than half a meter was required to withstand the earth and groundwater pressures of the overburden that will rise to some 60m above the tunnel horizon and impose a working pressure of up to 5 bar at tunnel invert and a potential 1.5 bar pressure difference across the face of the giant TBM.
CBE of France has supplied the segment production needs

CBE of France has supplied the segment production needs

The weight of each segment mould is seven tonne, and the largest of the standard segments weighs some 16 tonne.
In addition to the moulds, CBE also supplied an automated precast segment facility for setup near the construction site and from where almost 13,000 segments will be produced for the drive.
As part of the order CBE subsidiary Acimex designed and manufactured a segment handler and two segment erectors for fitting to the huge TBM to manage build of the massive segment lining rings. Both erectors will be fitted to the machine, but rather than working together to build parts of the ring simultaneously, the second erector will provide redundancy and backup so that progress can be maintained should the primary erector fall out of service for any reason.
Twin vacuum segment erectors will build the massive lining rings

Twin vacuum segment erectors will build the massive lining rings

Another significant contributor to the project is SolData, which remains busy installing the geo-instruments and data recording systems that will monitor ground movement as the TBM progresses under the hundreds of structures that lie on and below the surface of the alignment corridor. These range from city center high-rise office towers to the foundation piles of the elevated highway viaduct itself. The drive will also cross underneath the city's LRT/Bus tunnels, its railway tunnel, and Battery Street road tunnel, as well as under the many sewers, water supply mains and other buried infrastructure. The eyes of the world will be on this project as it progresses, and keeping the existing fabric of Seattle city intact will be one of the highest priorities for the reputation of the universal tunneling industry.
As the project continues and we learn of other industry equipment and materials producers contributing to this high-profile and prestigious project, TunnelTalk will bring you the news.
  • Mega bored highway alignment

  • Double deck highway configuration

    Double deck highway configuration

Mega EPBM arrives in Seattle - TunnelTalk, April 2013
VIDEO: Mega-TBM assembled and tested in Japan - TunnelCast, December 2012
Technical parameters of Seattle's mega EPBM - TunnelTalk, December 2012
Keeping Seattle safe on Alaskan Way TBM drive - TunnelTalk, February 2012
Alaskan Way contract signed - TunnelTalk, January 2011

Add your comment

Thank you for taking the time to share your thoughts and comments. You share in the wider tunnelling community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language professional.
In case of an error submitting Feedback, copy and send the text to
Name :

Date :

Email :

Phone No :

   Security Image Refresh
Enter the security code :
No spaces, case-sensitive