Though she remains very far from being done, Big Bertha completed a very important leg in her journey beneath Seattle last week, breaking through a thick wall of concrete and into a 12-story pit.
According to a report from the Associated Press, the world’s largest tunnel-boring machine moved 57 feet since February 17 to enter the pit. You can watch a time-lapse video of the massive machine making its way into the pit below. The video offers a rare glimpse to see one of these huge machines in action thanks to the cross-section of the earth the view from the pit provides.
The machine is nearly two years behind schedule in digging Seattle’s new State Route 99 tunnel due to a long list of setbacks. The massive machine went down only one-tenth of the way through digging the 1.7-mile tunnel which will carry a double-deck highway and replace the State Route 99 Alaskan Way Viaduct.
Water and sand clogging her cutterhead openings brought the machine to a halt, penetrating seven rubber seals meant to protect the main bearing.
According to a report from the Seattle Times, Seattle Tunnel Partners, the lead contractor on the tunnel, hopes to have the machine’s 630-ton cutterhead, drive axle and bearing to the surface by the end of this month.
In order to do this, the Times reports workers are busy inside the machine disconnecting hoses and electrical while others weld points to the outside of the machine where cables can be strung through in order to lift the pieces of the machine to the surface.
Once everything is lifted to the surface, workers will install 216 steel ribs and plates that will add 86 tons of reinforcement to the 7,000-ton machine’s drive block and cutter drive. The repairs are expected to be completed by April with hopes to resume drilling by August.