STB Flickr pool star Atomic Taco took some video two weeks ago:

You can watch the other 6 parts on STB’s YouTube channel.

44 Replies to “U-Link TBM Video”

  1. At 3:43 I see something with the word Traylor on it. Is that the same Traylor that worked on the old I-90 bridge?

  2. Is any of this work “interesting” enough to make it on one of those “Modern Marvels” or “Build it Bigger” type shows or is this work “ho hum” nowadays?

    1. I think the deep bore tunnel would be more appropriate for a show like that. The Beacon Hill tunnel had one of the deepest stations in the US (I think).

      1. Yeah, pretty sure China is the place to look for megaprojects these days. I suspect they build more subway before 9 AM than we do all year.

      2. An advantage to being a communist government with complete eminent domain, low property prices and probably no environmental process.

    1. The guy asking all the questions in the videos? I don’t remember him introducing himself. Maybe Zach remembers?

      Also, the guy in the blue coat is Mike Lindblom.

    2. You’d think that guy would have done at least a little research before showing up to look at the machine. He didn’t seem to have slightest idea how the thing worked or what he was looking at.

  3. I have a question about Ulink. In all the pictures I see of its path, why does it swoop down to make like a U, before heading up to Cap hill, and U District? Is this why it’s called Ulink? lol

    1. You might be looking at an old map that included the First Hill station, which was eliminated due to issues of productivity and construction risk. Current maps, like the following, don’t show any “U” like that:

      The First Hill Streetcar is primarily being built to make up for the elimination of First Hill from Link.

      1. I would have called it a C… and it’s nothing compared to the giant U that the old First Hill maps have. But I take your point.

    2. I read somewhere awhile back that it was to reduce the grade of the tunnel by giving it more distance to come up from Westlake/Convention place. Otherwise the Capitol Hill station would have to be even deeper.

  4. Ok, I do see that, but from under I5 to Cap hill station, it still makes this weird loop swing. Why doesn’t it just go in a straight line?

    Also on a side note, why not a counter on the side of the page for the First Hill Streetcar? That is very close when compared to Ulink. :)

    1. I suspect because they want to minimize the track curvature between those two stations. If they went straight (following Pine St) they’d have to make a sharp bend going in to Broadway Station; this way they have a small kink coming out of Westlake then a long gentle curve that can be taken at full speed. The other thing that occurs to me is that by doing it like this, they go under I-5 at 90 degrees, which minimizes the amount of dirt they have to dig out under I-5. Shoring up I-5 is a significant part of the cost of the U-Link construction.

      1. Digging under any pre-existing structure requires tremendous care, especially one built into a bank and subject to continual loading changes like I-5. See all the problems that the viaduct replacement tunnel is causing with some of the buildings downtown. That tunnel is much bigger, but also much deeper.

      2. Actually the digging under I-5 is done already. Remember when the exit to Pike Street was closed for a year? The difficulty was going through the Capitol Hill retaining wall and the deep pillars that hold up that wall.

      3. I think those structures are still there; the work was to reinfoce and rebuild them before the TBM goes through. On the other side of the freeway, they excavated and added controlled density fill (i.e., concrete without the aggregate) along the path of the TBM.

      4. @Kaleci Actually the construction that you are referring to was to strengthen the existing I-5 structures so that boring could occur under them.

      5. The cover between I-5 and the tunnel is just 13 feet, which, at least to a layman, sounds like not very much. Hence the shoring up, and minimizing the transit under I-5.

    2. It’s probably related to why Link is branching from Westlake station and abandoning Convention Place station. The engineers say it’s more feasable that way, that Convention Place station is at the wrong angle. Of course, when they built the station in the late 1980s, they put rail tracks in as an afterthought, but they didn’t really think about the exact route a future train would take from it.

      1. If memory serves me correctly, the Convention Stn thinking at the time, now 25 years ago, was to use the reversible lanes with buses (as they did), and use the tracks to convert some of the reversible lanes to rail, to at least the U-Dist (which got dropped). That was an early proposal by Kaiser Engineering, then was removed from discussion in favor of the Parsons team looking at tunnels under Cap Hill (Norm Rice, et al).
        I don’t have a clue who the responsible ‘string pullers’ of the day were, nor does it matter any more.

      2. I was wondering why Link is bypassing Convention Center station. Once Ulink opens, will the trains run through the station, just not stop at them?

      3. The trains won’t run through Convention Place at all, since it’s at the same level as the express lanes. You can see the U-Link stub tunnel east of Westlake Station, where the tracks branch off to go under the express lanes.

      4. Are there any pictures of this? IE the tunnel branching off? Or can you see it from Westlake station?

      5. You can see it from any bus going from Westlake to Convention Place. Sit on the right side of the bus and you will probably see a Link train parked in the branch tunnel.

  5. I still don’t understand how the TBMs are steered so that from the U-District, they will emerge onto the platform at Capitol Hill. Who is guiding the two machines?

    I did look on Wikipedia under tunnel boring machines and the cutter head can be angled which is fine, but who guides it as it moves forward?


    1. I would assume that the existing path of the tunnel is surveyed the old-fashioned way (with theodolites etc) and then the operator is told to angle the head whichever way it needs to go, left-right-up-down.

    2. Surveyors establish a few control points, which are located very precisely at a known point on the surface. This is a basic principle of surveying. During design, they figure out where to place the tunnel then translate that into instructions during construction. Using those same control points, they use a laser/optical target to ensure the TBM is on the proper alignment.

      This document explains one system in greater detail.

    3. And it would be a skill few people have. That is probably why it is expensive.

      Just imagine how quick the Cascade Tunnel would have been done if they had a couple boring machines!

      1. At about 2:30 in part 3. It would be helpful to read the document Oran pointed to first though.

  6. Thanks for the videos, Tim. I got to part 5 before I decided the ambient noise made it not worthwhile to continue. Is there anything of importance in 6 and 7?

    1. I don’t remember. I haven’t watched the videos–I took them so no need to see the same thing twice ;)
      Combined they are only 2:37, so not too much more to watch.

      And on the ambient noise–sorry about that. I knew it would be a problem–I for got my semi-directional mic (which is pretty crappy) and had to use the on-board mic.

      1. But thanks for recording them an posting them. I didn’t get a lot out of the final two, but I did watch all 7 and I appreciated them. I’ve seen some explanation of these machines and some animated videos, it was pretty cool to see them in person. And great of them to make the time available to you to go and see them and get kind of a tour.

  7. I like how Sound Transit has the ST wave on the side and the ST colors on the front…very creative. That thing could be gutted and converted into the biggest transit vehicle ever ;)

    1. I’d like to see what it looks like afterwards. Would it get pretty scuffed up or is it superbly precise?

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