I imagine that established TBM manufacturers already know.
A stepped pattern of heads with each one only grinding away the same volume at each consecutively larger ring could potentially be faster, but would get really long.
In the end engineering always comes down to three options: fast, cheap, or properly. Pick two.
Not really related, but just because it’s quite interesting:
You hit it with your fourth shot. The usual situation is that the TBM is sitting idle a good portion of the time, because spoil can’t be removed from the tunnel fast enough. The problem usually isn’t getting it out of the tunnel, but rather getting it away from the tunnel head. Most TBM’s are working in areas where the transportation infrastructure is a problem, otherwise, what need would there be for the tunnel?
Secondary issues are things like providing power, and having enough room to work behind the TBM (doing things like installing casing and pumping out the water).
There’s also the problem of keeping the city running while you’re dismantling and reassembling the underground services in the machine’s path.
Actual performance of the machine is very seldom the limiting factor.
Oh, and I almost forgot to mention the issue of getting the thing to the work site in the first place. The existing infrastructure often won’t support rolling such a thing on the rails or through the city streets. Just getting the machine in and out can be a bigger job than digging the tunnel.
RE Punny title:
About, Great Gob, 20 years ago a company that published a telephone directory did a series of great ads. They showed a funny scene, then a close-up of a Yellow Pages listing relating to it.
One of these showed a bunch of guys, I think in white lab coats, looking intently at this strange gizmo with gears and rotating arms. They stare and point and look absolutely fascinated.
Quick cut to Yellow Pages heading for Riveting Machines.
So, now we’ve found the opposite.
Do you know anything about the problems of over-excavation? I’ve read about sinkholes opening up in the properties on the surface, because they removed more material than the tunnel required. How can they tell if that’s happening, is it the ambient pressure at the cutting head?
Same deal with most earthworks.
When you see the roadbuilding crew standing around leaning on their shovels? They’re waiting for the asphalt truck to come back with another load. In the mines, a millisecond explosion is followed by hours of spoil removal.
In my job, we’re often working in a crew that consists of one guy with a chainsaw plus half a dozen working with their hands. Chainsaw guy crawls in and hacks at the bases of lantana etc, then the rest of us spend five minutes hauling away and smashing up the corpse.
Nobody minds chainsaw dude resting while we haul, because chainsaws are heavy and the protective gear (helmet, earmuffs, facemask, chaps, etc) is fucking hot and uncomfortable. And nobody wants to work near an overly-tired chainsaw dude.
People said pretty much that about rockets a few years ago.
A lot of those problems are that the material that overlies the tunnel is less cohesive than predicted. Sometimes in a fresh bore, you’ll get chips flying out of the walls as the rock decompresses. It’s nasty stuff. The engineers do what they can with seismic shots, ground penetrating radar, and what not, but once in a while, when you take out the rock, stuff on top is going to settle.
In the hiking clubs I’ve been in, there’s a lot of trail maintenance work. The minimum crew to serve a chainsaw is six (eight is better). You need the operator, the mule (the guy who carries the fuel, oil, wedges, and what-not for the operator), and at least four swampers (the guys who remove the spoil). That doesn’t count the crew who follow behind with brush cutters, McLeods, Pulaskis, whatever, to clear the stuff that’s too small for the sawyer to bother with. Even with a crew like that, the sawyer is idle most of the time - and that’s a good thing. I’d much rather be a swamper, a mule, or a sidecutter than have the hot, smelly, uncomfortable work of the sawyer.
Technical rock work on trails is more incredible stuff. The ballet of eight guys placing a 500-pound boulder to serve as a step or a water bar - likely shifting it with levers and a zip line - is a joy to watch.
All construction work is ‘hurry up and wait’ as raw materials are brought in and spoil is removed. Shifting bulk material is always the long pole in the tent.
Never underestimate how much a totally new start based on the current state of the art can improve things. Manufacturers, in this case of TBMs, typically have a long legacy behind their latest design, and that legacy often carries with it design decisions from very early generations.
It’s very hard to justify breaking with the legacy when you have a solid market. Only a new entrant can justify it (because they have to).
There is a mothballed one under Barcelona if anyone wants to hotwire it and make a very slow getaway:
The short answer is: rock is hard.
Anyway, if you are thinking about starting your own boring company, this is the place to get the equipment.
I don’t think he personally is going to dismantle the thing. He runs multiple companies. Presumably he’s going to assign engineers to do it. And who knows, maybe recent technical advances really will allow them to build a better boring machine. I kinda doubt they’re going to improve speeds three orders of magnitude, but I’m prepared to be wrong.
The media’s tendency to talk about him as a Heinleinian polymath superhero isn’t an accident, it’s part of the cult of personality that they perpetuate to sell copy and he doesn’t correct because it’s useful branding. But let’s not really believe he’s doing the job of hundreds of engineers in his down time between managing multiple multi-billion dollar corporations.
Something something rockets something return to land like some Heinlein story and reuse something something.
I keep joking with a friend at work about starting a pub for machinists; The Boring Bar.
The Mexican drug cartels have two dozen boring machines on order for when The Donald puts up his border wall.
They’d never leave because parting (off) is such sweet sorrow.
Please warn us when you are about to give a Walking Dead spoiler. I’m still a season behind.