Can I get help on how to make a foundation for an underwater dome that can hold an amount of 150,000 people? But don't try to use Wikipedia, please.

  • $\begingroup$ Normally buildings are designed in terms of employed materials, foundation ground type and consistency, maximum solicitation. Unless you define these your question is too broad. $\endgroup$ – L.Dutch - Reinstate Monica Apr 18 '18 at 16:36
  • $\begingroup$ Holding 150 000 people like a stadium? Or a city that includes everything from housing, workplaces, schools...? $\endgroup$ – Vincent Apr 18 '18 at 16:43
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    $\begingroup$ How much water is this dome under? A dome that's three miles underwater will require a vastly different engineering solution to one that's just three feet underwater. $\endgroup$ – F1Krazy Apr 18 '18 at 16:48
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    $\begingroup$ welcome. interesting concept that has been delved into in several questions on Worldbuilding SE. questions to help you define your problems a bit more: deep under water or shallow coastal water? rocky bathymetry or sand/clay bathymetry? have to take into account wave action or strong currents? are we using today's tech or far future? or possibly even past tech? Currently there is nothing defining what you are actually having a problem with or even how you would define an acceptable answer. I suggest you have a look around at other similar questions to see if they can help first. Enjoy :) $\endgroup$ – EveryBitHelps Apr 18 '18 at 16:58

Build it without a foundation.

Your air filled huge dome will have substantial buoyancy. It will have negative weight. It will not sit on the bottom. It will be like a huge helium balloon on land. A balloon does not need a foundation. You will need strong tethers to keep your dome from floating away.

  1. Sink deep pilings around circumference of dome site.
  2. Put some sort of floor on the site. It can be anything because it serves no structural purpose.
  3. Position dome in ocean over pilings. Fill it with water until it is barely buoyant.
  4. Winch it down into the piling nest. You will need to add air as it goes down because as it gets deeper air within will be compressed and it may become less buoyant.
  5. Once in position over floor secure it to floor and pilings and fill with air. If interior pressure is slightly over external that will ease the load on the dome from external water but you might blow it up off the floor. Internal pressure slightly lower than external will let water press the floor up into it and if it is close to external it is not that much load for the dome.

If you are so deep you need huge air pressure then your inhabitants will get nitrogen narcosis from the high pressure air. You will need to either use a helium oxygen mix or lower pressure air and hope your dome can take the external pressure.

  1. Watch to make sure pilings are not getting pulled up and loose!

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