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from the boring-doesn't-have-to-be-boring dept.
Brunel had his ships. Trump had his walls. And now Musk wants to make... tunnels, tunnels under cities to reduce traffic congestion and make the world a better, cleaner, less rage-filled place.
Over the weekend, probably while sitting in traffic behind the wheel of an autonomous Tesla, Musk tweeted: "Traffic is driving me nuts. Am going to build a tunnel boring machine and just start digging." An hour later, probably while still sitting in traffic, giving him plenty of time to think of a witty pun, he declared: "It shall be called 'The Boring Company.' Boring, it's what we do."
And finally, an hour after that, just in case any of us were foolish enough to think the billionaire multi-CEO was joking, Musk said, "I am actually going to do this." He also changed his Twitter bio to include "Tunnels."
So, unless Musk was suffering from a prolonged bout of entrepreneurial road rage, we now know roughly how long it takes a pedigree industrialist to pick a new disruptible domain: two hours, give or take.
Tunnels are indeed a pretty good solution for traffic congestion, though they take a long time to build, and the construction usually causes a huge amount of disruption above ground—especially if those tunnels are being built in a metropolitan area, which is where you'll find most of the world's congestion.
Depending on the setting, it can be very difficult and expensive to build tunnels as well. Cut-and-cover—where you dig up an existing road, build a tunnel, and put the road back—is the only "cheap" tunnel building method, but it's so incredibly disruptive that most tunnels nowadays are built at deeper depths by automated tunnel boring machines (TBMs). Cost-wise, you're looking at about £1 billion per mile for TBMs: London's Crossrail, with 13 miles of new tunnel, will cost around £15 billion; Manhattan's second avenue subway line, with 8.5 miles of new tunnel, will cost about $17 billion. The costs are much lower if you just want to bore through a mountain—the just-completed 35-mile Gotthard Base Tunnel through the Alps in Switzerland cost a mere £10 billion (and took 17 years to build!)—but I doubt Musk has those kinds of tunnels in mind.
(Score: 2) by VLM on Monday December 19 2016, @09:36PM
Why are TBM so slow?
Compared to what water cutting machines can slice off or lasers can vaporize or even just CNCs driven by powerful motors can cut, I've always wondered why a TBM doesn't move as fast as a waterjet cutter sometimes can. Why can't you have an array of redundant waterjet cutters on arms that drills and removes like a mile of tunnel per day?
Rather than crushing the rock hydraulically have 1000 simultaneous water jet cutters make 6 inch deep cuts thru granite every couple inches then a hydraulic arm or wedge bashes them off. Sure each cutter requires the full output of a 150 HP pump, and at 6 inches of granite its only cutting a couple inches/sec, but still...
Maybe if you had on board CNC torches and forge hammers continuously polishing the cutting head cutters you could go thru rock quicker.
Maybe the trick is diamond tip drills to weaken the rock in some kind of finite element optimized optimally weak configuration, then smack an existing cutting head thru it like butter making up for the drill delay.
I'm curious if the fundamental limit is shoving power to the cutting head, or is it some kind of vibration or guidance limit, or speed of material removal...
Classical TBM seems a boring (oh the pun) industrial technology that's ripe for disruption. TBM is like the slowest moving industrial-ish thing I can think of. If you're willing to take VC money and abandon the existing technology and blue sky something up, I wonder how fast you could make a hole using CNC and swarms of autonomous robots and frac-ing and water jets and lasers and who knows what else.
(Score: 0) by Anonymous Coward on Monday December 19 2016, @11:11PM
Think outside of the box: nukes!
(Score: 1, Interesting) by Anonymous Coward on Monday December 19 2016, @11:44PM
I'm not in the industry so I am just guessing, but I would guess it is the same thing which causes most perpetual motion machine ideas to fail: heat.
If you are removing 1000 as much material you are talking about 1000 (or probably more, physics tends to act in strange anti-synergistic ways) heat. You have less area to vent the heat as you are surrounded by rock with a high specific heat rather than air which can circulate. Plus you have all that material to remove.
There is also the question of how much energy you have access to.
For comparison, take a look at these two what-if XKCDs: #119: Laser Umbrella [xkcd.com] and what-if #135: Digging Downward [xkcd.com]
(Score: 2) by Capt. Obvious on Tuesday December 20 2016, @08:16AM
Where does all the water come from/go?
(Score: 0) by Anonymous Coward on Tuesday December 20 2016, @08:57AM
Another consideration is where they are digging.
Take something like this https://en.wikipedia.org/wiki/Second_Avenue_Subway [wikipedia.org]
They are using pretty much all of the ways of digging tunnels. They have about 1/8th of it done. It may even open in a couple of weeks. It took them about 5-6 years just to dig that one section.
Why? Well there is a city in the way. Existing tunnels, buildings, wires, sewage, etc. People do not like it when you cut them off or destroy their multi million dollar building. By either cutting through them or collapsing them.
Another consideration is the soil/rock they are digging through is not uniform. On the project I showed above they have at least 5 different types they are cutting through.
Then on top of that they have only so many people who can actually do the job. Those people are busy rebuilding the 9/11 stuff. Yep that is still being fixed. They could hire more but they also need to keep the budget down and not bankrupt the city while doing it. They are also building a whole 2 sets of levels under grand central. For storage, exchange and wait. Then trying to connect it up to an existing 90+ year old system for which finding parts is nearly impossible.
Oh and they are out of money at this point and need to issue more bonds to pay for the next 2 phases. Phase 4 probably will not happen for 15+ years.
(Score: 3, Insightful) by GreatAuntAnesthesia on Tuesday December 20 2016, @12:38PM
> Why are TBM so slow?
They have to stop every few dozen metres to hose all the balrog bits off the cutting head.
(Score: 1) by Francis on Wednesday December 21 2016, @12:33AM
A large part of it comes from the soil monitoring that goes on. You have to constantly measure the soil going out with the progress of the machine so that sinkholes don't develop. There's also huge amounts of pressure to begin with and over the course of the route, you can't deviate by more than a few centimeters. especially if the machine is planning on meeting up with another machine in the middle.
Also, tunneling through granite is rather unusual, if you've really got granite all the way, then tunnels are a poor design decision. If you're going through hard rock, then there's not much point in using a machine rather than having people do it.
(Score: 2) by VLM on Wednesday December 21 2016, @01:22PM
tunneling through granite is rather unusual
Its interesting to think about how a place like NYC got built because its a nice place for 1700s era sailboats to trade, although annoying to tunnel thru. The city site was kinda fixed before they decided to start digging tunnels.
Likewise it might be an interesting hard sci fi plot-line to figure out a reason to site a city where its actually a good tunneling area, and then figure out the logical (if any) conclusions.
(Score: 1) by Francis on Wednesday December 21 2016, @07:09PM
San Francisco and Seattle are a couple of other examples of cities being located in dumb places. Locating cities on top of so many large hills doesn't seem very efficient for moving goods and services about the city. Even worse prior to the invention of the automobile.
If you're hand digging tunnels, or really using explosives, hard rock is preferable as the tunnel isn't going to cave in on your. However, the softer soils are better with boring machines because they'll build the structural support behind them as they go.
And yes, that would be kind of interesting, but it would probably come down to some sort of dystopian nightmare, in which case, the authorities aren't likely to allow the city to be built there. Perhaps a moon colony would make the most sense as there's no protection against the sun's rays there.