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Comment by andyjohnson0 | Hacker News Reader

Interesting article. I was surprised by how mature and automated the technology was, given how relatively few tunnelling operations of this scale have been attempted.

Also, the concrete slabs, and presumably therefore the tunnel, have a projected lifespan of 120 years [1]. I wonder what use the tunnels will be put to in 2120?

[1] http://www.railtechnologymagazine.com/Rail-News/Concrete-seg...

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>I wonder what use the tunnels will be put to in 2120?

Being as the tube opened in 1863, I guess the same one :)

If it turns out that we're still using underground trains in 100+ years time then that would be interesting in itself. Hyperloop [1] maybe?

http://en.wikipedia.org/wiki/Hyperloop

Would it? We've been using basically the same electric subway technology for more than 120 years already. We might have something different in another 100 years, or we might not. Note that if anything, the pace of progress in mechanical arts is slower now than it was in the late 19th century.

What good is hyperloop for cross-city travel?

People in 1915 were I am sure imagining a future of personal flying machines which they were confident would be in operation by 2015.

Here we are, still cramming into the same tubes that people were travelling in (albeit probably less crammed) over 150 years ago.

Reminded me of a Peter Thiel quote reference in [0]: 'We wanted flying cars and instead we got 140 characters.'

Flying cars were a means to an end; we got a similar end, we just found a different means.

[0]: https://medium.com/@timrpeterson/140-characters-is-as-good-a...

Hyperlopp is very very low density comapred to a tube network. It would destroy the capacity

relatively few tunnelling operations of this scale have been attempted

More than you think, I suspect; TBMs are a fairly mature technology. Crossrail is not as impressive as the Channel Tunnel, which is a major feat of alignment as it was tunneled from both directions to meet in the middle.

"More than you think, I suspect"

That is very likely.

Wikipedia has a list of long tunnels [1]. And "Tunnel Talk" lists what the world's "mega TBMs" are up to [2] (frustratingly they quote tunnel diameters but not lengths). Seems like these machines are kept very busy, which makes sense given their cost.

Edit: Even more tunnel-related stuff at http://tunnelbuilder.com/

[1] http://en.wikipedia.org/wiki/List_of_longest_tunnels_in_the_...

[2] http://www.tunneltalk.com/Discussion-Forum-Mega-TBMs.php

Seems like these machines are kept very busy

I believe that many of them are actually single-use. Some (or perhaps all?) of the Crossrail TBMs are being buried at the end of their tunnel. Apparently the effort of removing them isn't worth their resale value?

That tunnel talk page does mention that several TBMs are being reused though so perhaps this is changing with newer/larger machines.

They operate in an extremely hostile environment, which takes its toll, and a bit like fighter planes there aren't enough built to make a consume-quality product. Some are reused but they'll always go through a major overhaul in between doing so.

At least one of the Chunnel TBMs was also driven in to its own grave.

If you do not take them out (which would have meant dismantling them and dragging the parts through kilometers of tunnel), they have to be, or they would block the tunnel they dug.

The article mentioned £10 million per machine which, as a complete layman in these things, I found incredibly cheap, even assuming maintenance costs would likely out-weigh the cost of the machines.

For recently completed tunnel in Gdańsk the machine cost was €21 million while the total cost for drilling operation was around €220 million

"makes sense given their cost."

OP indicates that the TBMs cost US$15MM each. I'm surprised they're so cheap. Those things are 50m long and full of complicated parts. It seems like the electronics and custom steel parts would cost that much and the actual design, construction, building, and testing the thing would cost several times as much.

At US$15MM, the labor to run them or even just to do maintenance would cost much more than the machines themselves.

The teeth need replacing often, even in the relatively soft gravel and clay below London.

I thought that sounded cheap too, especially for such a niche market where they can probably afford to mark up.

Yes it's a niche market, but the markup isn't there because the companies that make TBMs don't actually MAKE much of them. There are probably 100 or more companies that make the parts and the company that says "that'll be $15mm please" doesn't do a lot more than put together the design from the various parts and contract everything to be produced, manufactured, etc.

What they do have that you or I don't is contacts and business relationships with all the various suppliers and the knowledge of the myraid things that you need besides a bit spinny thing at the front, the conveyors that move the stuff out, and the hydraulics that move it forwards. In a very basic sense that's all a TBM is. But of course it probably does at least 20 other things that are absolutely vital to it functioning properly and efficiently.

But if a few senior guys decided that they wanted to work for themselves they could probably take enough supplier relationships and domain knowledge and start up another TBM company.

> Seems like these machines are kept very busy, which makes sense given their cost.

Interestingly, many TBMs are left underground forever, as it's often more expensive to disassemble and remove them then to just abandon them.

That's only done when you have a meet between two TBMs coming from opposite directions, and there's no way to get them out. Only for very long tunnels is that necessary. For most TBM jobs, you get the TBM back when it breaks though at the end of the job. After refurbishing, they're good for another job.

Go to TunnelTalk.com for the best deals on used TBMs.[1]

[1] http://www.tunneltalk.com/Equipment-Sales.php

The Gotthard Base tunnel (http://en.wikipedia.org/wiki/Gotthard_Base_Tunnel) is actually 7 kilometers longer than the channel tunnel.

When they connected the two holes the deviation was so minimal that it was quite impressive.

It will be used from next year, which is one year earlier than planned.

The channel tunnel wasn't even the longest tunnel even when it was completed over 20 years ago. (It was the longest underwater tunnel though).

> which is a major feat of alignment as it was tunneled from both directions to meet in the middle.

So was crossrail

The two ends of Crossrail "met" in a big prebuilt cavern in Farringdon. Still impressive, but not quite on the level of joining up two tunnels under the sea.

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