Meet Big Bertha - the world's largest tunnel boring machine

“Big” Bertha is the world’s largest tunnel boring machine. Right now, Big Bertha is visiting Seattle where she is helping the city create a two-mile long tunnel underneath of the city to allow some relief from the traffic aboveground.
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You would think it would be difficult digging a 2-mile-long tunnel underneath the city. But for Big Bertha, who is over five stories tall, it is just another day at work.
Big Bertha, named after one of Seattle’s first mayors, is 326 feet long, and not only digs the tunnel but also cleans up after itself, picking up the debris she leaves behind. Big Bertha can clear 35 feet per day. The debris is moved through the machine almost as if Big Bertha is eating the rock. It then travels along a conveyor belt where it is sent out the back of the machine to awaiting trucks for disposal. Big Bertha also installs the curved walls of the tunnel as she goes. In one pass, she bores the tunnel, takes out the trash and installs the walls, leaving behind a completed tunnel in her wake.
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The use of Bertha has not been without controversy though, as after drilling 11% of the tunnel she came to a long stop. It was later found that Bertha had hit an unexpected steel pipe, according to Popular Mechanics, requiring months of repairs. It was not until two years later that Bertha would be off and running again. The Seattle tunnel is expected to be completed in 2017.
Check out the video below for more information on Big Bertha, and SHARE if you like it.
Resources Popular Mechanics
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