How to safely construct deep underground harbors on a Snowball Earth?

A radical shift in the Earth's orbit has made the Earth much colder, with all the oceans freezing over, and the atmosphere liquifying and falling as rain. Humans live deep underground in areas of high geothermal potential, such as the Ring of Fire around the Pacific.

Apart from tunnels, they also want to use submarines in the deep ocean to transport people and goods around the world. Assume that the depth of freeze is currently at around 1 km.

Physics Question

First, with 1 km worth of ice pressing down on the liquid oceans, that's around 100 atm. In reality, I assume it would be somewhat less. First, water expands when it freezes, so it will be more like 90 atm of pressure. Second, I assume there will also be a "bridge" effect, with some of the weight of the ice mass being held in place by adjoining ice as opposed to "floating" on the water.

I have no idea how big this "bridge effect" will be. I assume it's not going to be big, considering that the oceans are thousands of kilometers across, but that's just a guess. Are there any better estimates? And approximately how much pressure will the water be under where the ice meets the sea floor at e.g. the California coast?

In other words, if you were to drill a hole down to the liquid ocean, how high would the waters rise - halfway to the level of the old sea level; almost all of the way; won't rise at all? (I'm guessing to perhaps 80-90% of the old sea level?).

Engineering Question

Second, am I correct to assume that harbor construction/operation will be potentially very dangerous for an underground civilization? As I see it, there are three potential harbor designs:

• Docking system (as in space): Submarine sidles up to a hatch, screws itself on, goods/passengers are exchanged. Failure mode: Hatch breaks/is breached.
• Lock gates (as in canals): submarine enters a chamber, gate behind it is locked in place, water level is reduced, submarine cruises to the next chamber. Failure mode: gates break.
• Compression chamber: in which there are no gates/barriers at all, but air is kept at a very pressurized state e.g. 80 atm to keep the water in place (this may be just about doable, as humans can work in up to 70 atm environments with the right gas mix). Failure mode: Decompression.

Of course, failures in any of these systems - assuming that the water is highly pressurized - will have an absolutely catastrophic outcome, as the pressurized water roars upwards and floods all the tunnels in the system... unless they are collapsed or otherwise blocked in time.

Is this correct? If so, what kind of safety measures will be required to operate harbors? I can think of just two obvious ones:

• Constructing the tunnels leading to the harbors in such a way that the lowest point at which they connect with the main network is above the old sea line (e.g., via a large elevator or funicular). So, even if worst comes to worst, only the harbors themselves will be flooded, not the entire tunnel system.
• Having many more redundant gates that can be slammed shut in an emergency on detection of flooding, explosive charges, etc.

Are there any other good, practical, not too costly (submarine travel would still need to remain competitive with tunnel transport to be of any use) safety features?

Or will this civilization deem harbors too risky and completely forego deep oceanic submarine travel?

Thanks in advance for your feedback.

posted about 5 years ago

ak7‭

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