- Client
- Washington State Department of Transportation (WSDOT)
- Project title
- SR99 Tunnel Project
- Builder
- Seattle Tunnel Partners (joint venture between Dragados USA, Inc. and Tutor Perini Corporation)
- Delivery
- Summer 2013
- Commence work
- Summer 2013
<Topics>
The world’s largest shield tunneling machine was officially named Bertha on December 20, 2012.
A naming competition for the world's largest shield tunneling machine was organized by the Washington State Department of Transportation (WSDOT). The winning name, Bertha, was submitted by a Washington elementary school student.
The naming ceremony was performed at Sakai Works by WSDOT representative Ms. Linea Laird on December 20, in conjunction with the completion ceremony.
Senior officials from the Washington State Department of Transportation
Completed SR99 tunnel (figure of image)
Shield tunneling machine in operation (underground)
Completed world's largest shield tunneling machine (figure of image)
- The slurry pressure system is designed to work with the variety of different soil types found in Seattle. Safety initiatives include injecting excavated soil with chemicals and using slurry pressure to prevent ground collapse.
- The new design allows cutter disks to be inspected and replaced from within the cutter head. This eliminates supplementary construction processes and allows the work to be completed safely at atmospheric pressure.
- Above-ground safety is of paramount importance because the machine will tunnel directly beneath a city. As such, the tunneling machine features a range of safety features.
- The tunneling machine has been split into sections weighing as close as possible to 900 tons, the maximum allowed under local weight regulations, in order to minimize the number of sections and speed up the assembly process in Seattle.
