Friday, September 26, 2014

Bertha: "Take Two Aspirin..." (Updated)

"Take two aspirin and call me in the morning!" A worn-out bromide that recommends a cure for a common headache.

But what is the cure for a US$80 million Earth Pressure Balance Tunnel Boring Machine (TBM), stalled 60 feet (18 m) below the surface between South Jackson Street and South Main Street in downtown Seattle?

On December 6, 2013, Bertha stuck when she chewed into an 8" (20.3 cm) 191-foot (58.2 m) pipe. The pipe driven into the ground by the Washington State Department of Transportation (WSDOT) to monitor effects of ground water on the Alaska Way Viaduct, damaged by the 2001 Nisqually earthquake.

There followed a heated exchange between Seattle Tunnel Partners (STP), and WSDOT. WSDOT claiming STP had been warned of the existence of the casing.

"The well site was listed in reference materials provided to bidders as part of the contract specifications. I don't want people to say WSDOT didn't know where its own pipe was, because it did," said DOT spokesman Lars Erickson. However, Chris Dixon, project director for contractor group Seattle Tunnel Partners, said the builders presumed there would be no pipe in the way, because casings are customarily removed after use."
(Seattle Times, Jan. 3, 2014)

When Bertha choked on the pipe, she had only completed 1,019 ft (311 m), a mere 11%, of the total 9,270 ft (2,830 m) length of the tunnel. Coincidentally, the warranty on the machine expires at 1,300 ft  (396 m).

On January 28th and 29th, Bertha crept forward a measly 4 feet (128 cm).  She overheated and has been shut down since, at 1,025 feet (312 m).

On February 11, Chris Dixon, Project Manager of Seattle Tunnel Partners (STP) and Todd Trepanier, Program Administrator for client Washington State Department of Transportation, WSDOT, discussed the possible causes and solution.

Last word is (2.21.2014) that STP will excavate a retrieval shaft to remove the 887 st Cutterhead to access the main bearing.  I give a detailed example of a similar retrieval shaft in the following segment.

Digging a retrieval shaft will be a costly time consuming episode, which will impact the completion date, and multiply construction costs.

History Repeats Itself

Bertha's "condition" is not the first time TBM operators have been faced with the challenge of accessing and repairing machines mired beneath the surface.

Canadian National railroad commissioned a tunnel in 1993, to replace the St. Clair River tunnel, to allow passage of double-stack rail cars.

Completed by the Grand Trunk Railroad in 1891, it was the world's first submarine tunnel connect, connecting Sarnia, Ontario, under the St. Clair River, to the boy-hood home of Thomas Alva Edison, Port Huron, Michigan.  And in doing so, established the first interchange between Canada and US.

The replacement tunnel was bored parallel to and approximately 27m north of the original tunnel.

CN self-funded their Earth Pressure Balance Tunnel Boring Machine, cleverly named "Excalibore." The TBM was manufactured by Lovat Tunnel Equipment, Inc., located in Toronto. (Later purchased by Caterpillar, who shut the plant down.)

In late 1993, difficulties were encountered with the TBM. Like Bertha, the main bearing faulted,  necessitating  removing the Cutterhead to replace the main bearing.  Fortunately, the TMB broke down before diving beneath the St. Clair River.

Complicating the repair, the TBM was 95 feet (29 m) beneath an oil refinery!

The TBM Cutterhead was 31 feet (9.5m) as compared to Bertha, 57.5 feet (17.45m). This required a retrieval shaft 33 feet (10.0 m) by 12 foot (3.7m) to access the Cutterhead.

To replace the main bearing delayed the project by 7 months, costing US$4.2 million.

This paper details the design and construction of the retrieval shaft from the viewpoint of the specialist contractor and consultant charged with its execution. This is what will take place to repair Bertha.

The Saint Claire River Tunnel was successfully completed in 1994. Here we witness a northbound CN freighter descending into the tunnel, next to the original tunnel portal. I still get upset at the lack of a caboose. The caboose was like a period at the end of a sentence.

When we refer to Bertha as the "World's Largest Tunnel Boring Machine," we mean it! This High Definition video, released in December 2013, produced by TunnelTalkVideos, takes us inside Bertha. It is absolutely awesome!

And observe the "mine field" Bertha has to navigate in the early phase of her 9,270 ft (2,830 m) length. The "Railroad Tunnel" is the Great Northern Railroad tunnel (now Burlington Northern Santa Fe.)

Don't forget, to enjoy videos posted on Oil-Electric, click on the "Full Screen" icon on the YouTube toolbar. To return to "normal" screen, merely tap the "Esc" key on your computer keyboard.

Type "Bertha" into the Blog Search Engine in the right hand margin, to access all articles posted thus far.

1 Comments - Click here: said...

Robert, I knew that you would deliver "the rest of the story" on Bertha, many thanks for all the research, great job!

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