Under the Sea

Okay all you engineering types and actual engineers and mathematicians and anyone else really.

Would it be possible to make a tunnel deep underneath the sea floor extending from the East Coast of the United States to say Spain or the Azores or some point due east?

If not, why?

If nothing else, the mid-ocean rift where the plates are pulling apart from each other is going to be a problem.

Possible to build underneath the rift and circumvent the problem or build around plate shifts?

You’re trying to build a tunnel from the North American plate to the Eurasian plate. There’s no going around it, since you have to cross the boundary somewhere. If you want to go under it, then you’re running your tunnel through the mantle, which is a bit more difficult.

The rift movement is less than one inch per year. Possibly you could account for this with telescoping sections of tunnel that have a sliding seal; two yards of sliding capacity would give close to 100 years of service.

Alternatively, you could deliberately construct your tunnel in a zig-zag fashion and support it on sliding mounts, allowing the whole thing to flex like a coiled spring as the rift separates. The Trans-Alaska Pipeline incorporates both of these features - the zig-zags allow the pipe to cope with thermal expansion/contraction, and together with the sliding mounts in some locations, they can cope with seismic displacement.

The depth would make things difficult. water two miles deep means a bottom pressure of maybe 5,000 psi. Industrial hydraulic systems commonly operate at pressures in this range, so sealing shouldn’t be too difficult - but for structures as large as a tunnel, the walls will need to be extremely thick to prevent implosion.

Short tunnels rely on piston effect for ventilation. Longer tunnels typically have vent shafts with fan-driven flow to assure adequate fresh air. This is going to be a problem for your trans-Atlantic tunnel, since it won’t be feasible to run vent shafts to the surface, and it’s going to be hard to bring fresh air all the way to the middle of the tunnel.

Electric vehicles could minimize the need for air in the tunnel, but how to get the necessary power in there? high-speed trains these days appear to operate on 25-30kV, but they’re never more than a hundred miles or so from a power plant. A wire run of 1800 miles (to the halfway point from each end) at 25kV is going to incur substantial ohmic losses; your train won’t be very efficient. Cross-country transmission lines operate at several hundred kV for efficiency, but you isolate/insulate them by running them high up in the air, which isn’t going to be practical in the tunnel.

Seems to me that it would be possible to build this tunnel, but not remotely desirable. Expensive, time-consuming, potentially unreliable, and slow. High-speed trains are good over distances of a few hundred miles, but since they only run at about 200 MPH these days, a 3600-mile trip would last about 18 hours (versus 6 hours by plane). Some people are afraid of flying, so planes aren’t an option. For them, the choice would be cruise ship on the water for a couple grand, or a tunnel two miles under water for $$15,000 (hey, somebody’s gotta pay for this thing…). And if they’re afraid of flying, how are they going to feel about being in a tunnel crossing a seismic zone, surrounded by 5,000 psi of water?

Great post overall. But this comment leaves out the need for emergency access/egress. Of course it’s not practical to expect people to walk out of such a long tunnel in an emergency either. Maybe suicide booths positioned every 1000 yards so at least they have a quick end? (just kidding, really)

Well, ignoring the plate rift - to built the tunnel you’d have to go lower than the lowest depth in the atlantic (which is about 9km or so. So your tunnel would have to be drilled to a depth of ~9km at some point.

The deepest hole ever drilled, which is a tiny shaft (on the Kola peninsula) is 12,000m deep, however the deepest “human sized” hole I know of is about 4km deep (a mine in South Africa).

Now, it might be possible to create a route avoiding the deepest trenches, (av. depth of the atlantic is ~3,9km) but that would still be several km deep. So you would basically have to somehow improve the tech used to drill a tiny shaft, and scale it up to the level of drilling a tunnel - for about 6000km.

So I guess this is one of those not even theoretically possible things - the manpower and cost involved would probably exceed the combined world output.

:smack: I totally missed that the OP wanted to locate his tunnel not just under the sea, but under the seabed. I was thinking of something like the Ted Williams Tunnel in Boston, where the tunnel walls are entirely manmade and sit on the seabed. Using natural rock as tunnel walls will be problematic for dealing with the movement of the rift - and given that the sea bed is seismically active, I wouldn’t trust the rock walls to be watertight to any useful degree. Maybe for this middle portion of the tunnel you could use manmade tunnel segments that telescope within each other to bridge the rift?

The Puerto Rico Trench has the 9km depth you mentioned, but this doesn’t appear to be anywhere between NYC and the Azores.

Also, we’re boring a tunnel, not a well shaft, so the tech is different. We don’t need a drill shaft several miles long pointed straight down, we just need a tunnel boring machine that starts on land a few miles from shore and angles down from there to stay a useful distance below the sea floor all the way across. This is how the Channel Tunnel was built.

You wouldn’t need air in the tunnel if every carriage had an oxygen supply. Rescues would be an issue either way.

I think a more sensible route would be a near great circle route: Canada to Greenland to Iceland to the Faeroe Islands to Scotland or Norway. You’d cross the continental divide overland, in Iceland.

If West Africa were not such a shit-hole I’d also suggest a link between Fortaleza in Brazil and Conakry or Monrovia in West Africa, perhaps via Ascension Island.

No. Just…no. This is theexact same question as “Is it possible to just tunnel through that active volcano?”

That “just” is one of the bigger leaps of hyperbole for the day. And this is a day Trump and the others are speaking :slight_smile:

It’s “just” a TBM … trailing up to 3000km of power cables and conveyor belts behind it to remove the waste rock. Buying the conveyor belt alone will bankrupt Europe.

This whole project makes me think of the Tsiolkovsky Rocket Equation. The infrastructure becomes 99.999% of the project & the payload is the last 0.001%
The thing I like best about the OP’s wacky idea is that when he gets done he’s got a tunnel to the Azores. WTF? Then from there you board an airplane or ferry boat for the last 850nm to Lisbon. Sweet!

Also of course, going due east from anywhere on the US east coast is not the short way to Europe. When we leave Miami for Lisbon we fly roughly East-Northeast and slowly turn right peaking about halfway between Nova Scotia & France then slowly curving farther southerly to arrive at Lisbon going roughly Southeast. That’s the short way.

No argument from me there. The OP was asking whether this tunnel would be possible, which I took to mean can it be done with current technology if we throw enough resources at it. abel29a suggested a technological problem related to limitations on how deep we are able to drill holes; I only meant to point out that we’d be drilling tunnels instead of wells. I offered the Channel Tunnel as an example to show that the necessary technology has already been successfully employed, but I realize this is a bit like if Robert Goddard had said in 1926 after his first successful rocket test, “now we can conduct a manned mission to Mars.”

The OP has not asked whether such a tunnel would be practical or economically justifiable, but I think we all agree it ain’t.

I agree & totally get where you’re coming from. The word “just” just caught me funny.

This thread got me curious about how you navigate when you’re boring a tunnel from both ends to ensure that both teams meet up in the middle. Rather than start a new thread, I’ll just stick the link here:

How do you make sure the two drills of a tunnel meet?

Are you suggesting carrying all the oxygen for the combustion of fuel as well? Obviously, the train is lighter if you only carry oxygen for the passengers and mount a sail on the train with a big fan back at the starting point (which also gets around needing to have an electric rail or catenary the entire length of the tunnel.)

(no, not serious)

I guess that the obvious answer is to build a Gravity train. No power needed, just a system to keep the carriages stable and to supply air for the passengers.

Of course there is the small problem of making a tunnel lining capable of withstanding around 5,700 K, and pressure of about 330 to 360 gigapascals.

The idea has been around for 350 years or so, so you might think that these problems would be solvable.

So I’m assuming a tunnel capable of getting in your car and driving underneath the Atlantic would be a no-go? (Not even plausible?)

The tunnel is a 3,000 to 5,000 miles long depending on where the ends are. IOW, it’ll take you 2 to 5 days to drive the length of it.

So the tunnel would have to include hotels with big parking lots every few hundred miles. And rest stops every hundred miles or so. And there’d need to be trucks bringing in supplies for the hotels. And ways to bring in electricity & fresh water & fresh air. And ways to pump out sewage and garbage & not-so-fresh air & car exhaust.

And all of this has to be built underground under an ocean thousands of miles from the access to the outside world.

The people who work at the hotels & restaurants & such would be a 1 or 2 days’ drive from the tunnel ends. So they’d probably be stuck living down in the tunnel for weeks at a time. Which means they need a place to sleep and a someone to work to feed them too. And transport then to/from work.

Nope, not gonnna work to drive through it that way.
A Euro- or Chinese-quality high speed train would still take 1+ days to get across. But at least it can carry sleeping & eating & bathroom arrangements along in the train. And these can be replenished up on the surface after it gets to the other end. So we don’t need a separate supply process inside the tunnel.

Couldn’t you just create the hotels under the sea floor and have off ramps going down from the tunnel into the area where the hotel would be?

As for workers you could ideally do what Dubai has done and have migrant workers from India and developing countries work in the service industry for low wages in order to boost your infrastructure along the route.

Could this be a viable way of decrowding over crowded areas by opening up transit links under the oceans and building houses on the off ramps and mini cities under the sea floor?

Think of all the jobs this project would create!

This looks like a project for Donald Trump!

You could ask the Washington Department of Transportation for advice and counsel on this one. They currently have the largest boring machine in the world sitting idle for the last year or so because things keep going wrong. It’s taken this magnificent machine almost three years to go a little over 1,100 yards.

Let’s see now, the Atlantic is how wide?..

I predict we’ll have faster than light transportation or teleportation before we get a tunnel under the Atlantic.