Sunday, March 8, 2015
This is an exact replication of the “rescue” of “Excalibore,” Canadian National’s Tunnel Boring Machine that broke down under an oil refinery in Sarnia Ontario in 1993. Only “Excalibore” was less than one/half the diameter of “Bertha.”
Bertha just completed boring into the rescue pit, where a gaggle of workers will dismantle the Cutterhead, returning it to the surface for repairs. And so far, she is more than 18 months behind schedule. The original Timeline projection for completion of boring reflected September 2014.
Work began on Friday to attach lifting eyes to Bertha for extracting the machine from the rescue pit.
I’ve compiled a series of YouTube clips, that bring us up to date.
Remember to click on the "maximize" button to view the YouTube video in full screen.
• Bertha Tunnels Toward Repairs. As Bertha’s Cutterhead chews through the concrete piling of the rescue pit, spoils are shuttled by conveyor belts the length of the tunnel, across former Alaskan Way to Pier 47.
Here the spoils are loaded onto a barge, to be delivered by Foss Maritime, for disposal in a former borrow pit located at Mats Mats Bay.
• Bertha Reaches Daylight, February 19, 2015. A final exciting moment as Bertha gnaws into the rescue pit. In preparation for the break through, a hydraulic pick chiseled out a notch to create a clean entrance into the pit. One is struck by the slow speed of the Cutterhead! Remember, it stands ~5 stories high and weighs ~900 tons, driven by 24 dc motors!
• Bertha Pushes into the Rescue Pit. Time lapse of Bertha positioning herself on the rescue cradle. Notice the articulated joint on Bertha, just inside the pit. This facilitates pin point steering of the TBM. guided by GPS and Laser measurements. (Thanks, WSDOT!)
• Chris Dixon, spokesman for Seattle Tunnel Partners, explains the process of retrieving and repairing Bertha.
• Building a Super Crane. As we’ve just witnessed in the animation clip, a large lifting device will be used to disassemble Bertha’s business end, laying the various segments out for repair. Such devices are “purpose built” for the job at hand. This Mammoet crane has a lifting capacity of 2,200 tons. You may recall the Cutterhead weighs in at nearly 900 tons.
The “Mammoet” logo was not added until the crane had been in place for a few days. I was unable to capture the individual applying the logo to the frame!
In addition, boxes of parts and upgrades to TBM components have been stored in a nearby warehouse.
While Bertha has been displaying her temper tantrum, Seattle's Sound Transit TBM's have been busy in the North End of Seattle, burrowing rapid transit tunnels, including a dig beneath the Lake Washington Ship Canal, with a striking absence of headlines!
Twin tunnels, more than 11,000 ft (3.35 km) in length, have been completed without a hiccup. Here is a time lapse walk from Montlake (University of Washington "UW" Station) through the tunnel to the Capitol Hill Station.
“The two TBMs that are digging from UW to Capitol Hill were named Togo and Balto after famous Huskies - the four-legged kind. "Togo" and "Balto" were canine heroes of a grueling sled dog relay to deliver medicine 674 miles from Anchorage to Nome, Alaska during a diphtheria outbreak in 1925. This amazing journey is commemorated each year with the Iditarod sled dog race.
“As they traveled south, Togo and Balto reached depths of up to 300 feet underground and had to withstand up to almost five times normal air pressure!” (From Sound Transit)
In addition, TBM "Brenda" is boring 4.3 miles north of the University of Washington Station to Northgate Mall.