Exciting boring video

This video from Herrenknecht AG shows the operation of the enormous tunnel boring machine that will conduct the deep tunnelling for San Francisco's new subway lines. The machine obviates the necessity of tearing up city streets for subway construction, and somehow manages to be gentle enough to avoid shaking the buildings above it. There's a much older version of this monster on display at the fabulous London Transport Museum in Covent Garden that is truly awesome to behold.

A TBM consists of a rotating cutterhead within a cylindrical steel shell that is pushed forward along the axis of the tunnel while excavating the ground through the cutterhead. The steel shield supports the excavated ground as required until the final tunnel lining is built in the rear of the shield. The shield is propelled using hydraulic jacks that thrust against the erected tunnel lining system. The TBM is used in conjunction with a prefabricated ground support system, which consists of pre-cast concrete segments that are bolted and gasketed to form a watertight lining.

Pressure-face TBMs that are capable of exerting a balancing pressure against the tunnel face are used to control excavation rates and groundwater inflow, as well as to maintain stability of the tunnel face.

After completion of TBM excavation and installation of the lining, the temporary rail and conveyor system are removed, the invert is cleaned, and a flat invert for the permanent rail fixation and a raised walkway are constructed as reinforced, cast-in-place concrete. The invert contains embedded pipes and inlets for track drainage.

(Thanks, Fipi Lele!)


    1. In order to avoid giving the impression of any kind of cultural or enthusiastic bias (such as pop music, rock, world, jazz, classic etc.) which could offend the taste of some stakeholder, you have to find music that is devoid of any of the characteristics usually found in music. As a result you end up with the equivalent of airport or elevator music, a kind of soothing ambient noise designed to be nothing whatsoever.

  1. A-mazing. Thanks, Cory. Somebody tell me how they get this EPB into the ground. Excavate, lower, assemble and go?

    1.  TBM’s are assembled on site inside of a launching pit (generally reused as station boxes).  In Barcelone the tunnels were large enough to actually house the station platforms.  So the only surface excavation was an approximately 100′ diameter shaft down.  I have a picture somewhere of a TBM breaking into one of these shafts.  I will try to find it…

  2. I’m a tunneling engineer, TBM’s are why I got into tunneling!  They are amazing machines and going inside one never gets old.

  3. When Seattle had its bus tunnels bored, they had the machine on display for awhile. This video helped me realize I only saw the machine’s head, not the entire engineering masterpiece.

    1. As Benjamin Franklin said, “If we don’t all drill together, we will surely drill separately.”

  4. Really makes you appreciate all the work that Lex Luthor had to do every time he used one of these to get out of jail.

  5. The last time I used “obviate” I got more abuse in return than the time I told someone not to be so niggardly.  I guess if you’re a professional wordsmith you can get away with using proper English!  I’m jealous.

    1. Words are cool… Don’t let dumbarses spoil your fun. The best fun is had in using uncommon words in group situations and watching people squirm as they try to reply without actually knowing what you said.

    2. We would be oh so gay if words were used for good and not just to titillate us.

  6. One of the most fascinating, and frequently exciting, books I ever read was Tunnels, by Gosta Sandstrom, about the days when people were first learning how to build really long tunnels. Some of the stories, especially about massive tunnels through the Alps constructed entirely by drill and blast  and caisson techniques are truly hair raising. Tunnel boring machines did away with all that. Now constructing tunnels is just very very tedious work.

  7. I applied for a job I am well-qualified for as a geologist attached to tunneling projects, in China. Sounded awesome – tunnels and TBMs and China all fascinate me. Never heard back from them; bummed me out.

  8. To paraphrase Richard Feynman, there’s plenty of room at the bottom, or just beneath our feet. It’s interesting to see SF is again taking the lead it once had in tunnel construction with the world’s leader Bechtel having it’s home there as it still does. The gigantic tunnel through Yerba Buena Island that connects the Oakland and SF sides of the Bay Bridge is still one of the engineering marvels of the age and shows that tunnels can be more than just worm holes suitable for walkways and narrow guage commuter trains. Anyone familiar with the city knows that its high aspect landscape has quite a few tunnels, some dating to the early days such as those around Ft Mason, and might suspect that it would be even better with a lot more. Think how nice VanNess, Franklin and Gough would be if no Highway 101 traffic was clogging it up all day and instead was travelling beneath Cathedral Hill…or if the Sunset were connected to the Bay Bridge via tunnel.  Returning local streets to pedestrians and allowing business to thrive along the busy streets instead of having to hide from the noise, fumes and danger of busy surface streets will be a great benefit to SF and to any other city that can do the same.

  9. My inner geekdom comes out.  I found this fascinating.  It’s a detailed break down of how large tunneling machines (TBM) work.  They are freaking huge!  One question I have that wasn’t addressed is what if they start tunneling through and archeological sensitive site like Pompeii or an old Shakespearean theater?  Are there monitors or something for the composition of the excavated materials?

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