Underneath Seattle: Steering Bertha

There’s no GPS underground, so how will Bertha, the SR 99 tunneling machine, hit a precise target nearly two miles from her launch point at the south end of downtown Seattle? One of the tunnel boring machine (TBM) operators takes you underneath Seattle to show how it’s done.

[@irvinwittmeier5208]

It takes a real man to be in charge and give all the credit to every one else!;-) nice job

[@artsbest1]

An incredible engineering feat.

[@weedandwine]

Built an 8 mile Cascade mountain rail tunnel 1925 to 1929. Working from each end they met up perfect in the middle. No computers or laser guided controls, just dynamite and shovels.

[@riparianlife97701]

The ring is built against a movable sleeve that trails the TBM. And as that sleeve moves forward, it leaves a small space between the outside soils and the outside of the tunnel rings. That appears to be the only chance for settling.

[@riparianlife97701]

If this works out, we need a pair of express tunnels the same size running under I-5 from the 405 to the 405.

[@dovemfg]

They forgot to mention that it’s powered by a nuclear reactor

[@702Demon]

Does this machine make a disturbingly loud sound when it hits certain rocks?

[@jaredrizzo8343]

Does anyone notice the concrete cracking when they are pushing on it from

[@WilliamAlanPhoto]

*sings

[@Levi-qu8yl]

What if a car gets in an accident inside the tunnel and explodes? Will the fire spread and trap everyone inside, ultimately killing them. Doesn't seem so safe.

[@heru-deshet359]

Bet they were paid more than minimum wage.