Meet Big Bertha, The World’s Largest Tunnel Boring Machine (TBM)

If you followed our story on what went wrong during Seattle’s SR 99 tunneling project, then you’re no stranger to Big Bertha, the world’s largest tunnel boring machine (TBM).

But if you missed it, or wanted to find out more about who made it and how it works, then you should continue reading!

Let’s start at ground zero:

  • Big Bertha was manufactured and supplied by the Hitachi Zosen Corporation to Seattle Tunnel partners for the SR 99 tunneling project.
  • It measures 57.2 feet (17.5 m) in diameter, which makes it the largest tunnel boring machine in history. To put in perspective, it would take about 10 average sized men standing on each other’s shoulders to stretch across its diameter.
  • It was delivered to Seattle from Japan, by ship, in sections, back in March of 2013 on a really big ship, with each section weighing approximately 900 tons (that’s the equivalent of 137,461 African Bush Elephants, WOWZERS!) which is the maximum weight allowed under Washington State regulations. Being sections also helped speed up the assembly process once the machine reached Seattle.

Bertha is filled with cutting edge (no pun intended) tunneling technology and safety features; as one would expect for its size and weight.

Though there were some known boring setbacks along the projects progression, however, Big Bertha eventually completed the SR 99 project back in April of 2017. SUCCESS!

To mark the historic project, a naming competition was held by the Washington State Department of Transportation (WSDOT) – who funded the SR 99 project.

The name Bertha was submitted by a Washington elementary school student and it’s safe to say it’s extremely fitting given the scale of the machine itself.

So now that you and Bertha are acquainted, if you’re interested in reading more about the specifics of how she works, or seeing some awesome pictures of assembly, head over to the Hitachi Zosen Corporation’s blog and get ready to get your mind blown.

The only question that remains now is “how much bigger can these machines get?”

Guess, we’ll just have to wait and see!

 

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