For anyone wanting to get a peak under the shield of Bertha, the 57.5-ft-diameter tunnel-boring machine that dug a 1.7-mile tunnel under downtown Seattle, now is the time. As work continues to disassemble the 8,000-ton, five-story machine, Bertha’s shield has been fully removed, exposing the inner-workings of the machine.
The upper shield that surrounded Bertha is now completely gone, cut with torches, lifted up and hauled away. And on Friday, crews removed the remaining pieces of Bertha’s cutterhead from the rest of the machine, really showing the progress that contractor Seattle Tunnel Partners has made in clearing the machine from the north portal near the Space Needle where the machine came to rest following its journey under Seattle.
Next, crews plan to remove work-deck platforms, hydraulic systems, hyperbaric equipment and ring-building equipment.
Bertha broke through to the north portal in early April, giving crews just over two months of dismantling the machine at this point. Washington State Dept. of Transportation, the project owner, created a brief time-lapse video showing what seven weeks of nearly non-stop work looks like as workers continue to dismantle the machine. View the video here.
As work on the machine continues in the pit, disassembly progresses from inside the tunnel moves forward as well. Seattle Tunnel Partners puts a focus on removing the trailing gear from inside the tunnel and has disconnected temporary utilities and ventilation necessary for the machine’s operation. Crews will remove those pieces through the sound end of the tunnel.
Inside the tunnel, crews work on far more than getting rid of the trailing gear. Seattle Tunnel Partners has now completed 66 percent of the southbound roadway. In all, the roadway in the tunnel will stretch 9,270 ft. The corbels—wall foundations—are 84 percent complete and nearly at the rear of the tunneling machine. Work progresses on the southbound and northbound walls as crews ready the double-decker roadway for opening in 2019.
Follow Tim Newcomb on Twitter at @tdnewcomb.