When the world’s largest tunnel-boring machine is involved, nearly every step of the way provides intriguing theater for the viewing public, especially when construction crews have to take unexpected steps to resolve issues.
Such was the case with the front-end repair of Bertha, the name for the TBM, recently completed in downtown Seattle. With aboveground repairs done, crews from Mammoet successfully lowered the 2,000-ton front end from its repair platform into the 120-ft-deep access pit over the course of two days.
Contractor Seattle Tunnel Partners has since reconnected the tunneling machine’s front end to the section that remained in the pit during repairs. With the two sections of the machine now bolted together, crews from Mammoet have unhooked the front-end piece from the custom-built red crane that performed the lift.
Significant work remains before the machine can tunnel again in late November. Three large pieces of the machine’s outer shield will get lowered into place for reassembly in the coming days and crews must also weld the pieces together. Beyond that, crews have the lengthy task of reconnecting the hundreds of wires and hoses integral to the machine’s operation.
Following the reconnection of every item, Seattle Tunnel Partners and the machine’s manufacturer, Japan’s Hitachi Zosen, will conduct a series of tests.
Every step signifies a big move, especially if the machine starts tunneling again in November.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.