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underwater viaduct

Underwater viaduct for tunnels over underwater canyons
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Some proposed underwater tunnel connections are unfeasable because there's a deep sea trench in the way. On land we would simply build a viaduct over a canyon, so why not do the same when building a tunnel?

I would propose a tunnel running under the sea floor up to the trench's vertical ridge, where it will emerge from the sea floor and become a covered viaduct or above-ground tunnel (or maybe I should call it a vunnel?).

Also. for places where building any kind of conventional tunnel would be hard, but where a building bridge would also be cnstrained by shipping or wind, a full underwater viaduct can be the best solution.

The underwater viaduct thus has the potential to allow for widespread usage.

sdk16420, Sep 22 2014

Bering Strait Bridge [pocmloc, Sep 22 2014]

I did the math for buoyancy https://app.box.com...yopwwxb64csy603btck
thanks all. porpoise, maybe the current effect can be reduced by using a more hydrodynamic shape than just a round tube, for example a double teardrop cross section. Another potential burden is the effect of buoyancy. If you have a 10m inner diameter tunnel, and a one meter thick reinforced concrete shell, then you still have to somehow compensate for 29 metric tons of buoyancy per meter. But this can also be an advantage, since holding it in place with cables to prevent it from floating might be cheaper than building heavy concrete pillars every 10 meters. [sdk16420, Sep 23 2014]

Beaufort's Dyke http://en.wikipedia...i/Beaufort%27s_Dyke
Projects for a tunnel or Irish Sea fixed link ... have been suggested .... The Dyke has always been an important problem for such proposals [8th of 7, Sep 23 2014]

Force of sea currents https://app.box.com...it66hike9o6y9t54hzg
Here's the updated pdf with calculation for the force exerted by the sea current added. I get 11 kN of horizontal force per meter of tunnel length. [sdk16420, Sep 25 2014]

Norway plans to build on http://inhabitat.co...er-traffic-tunnels/
Hah! [sdk16420, Jul 25 2016]

[link]






       If an ocean current is 10 times slower than wind (100 fold less energy), it's still 1000 times more dense. From an energy perspective, this means an underwater viaduct would have to be 10 times stronger than a land-based one. That neglects viscosity and other fluid dynamics stuff that you need charts for, but I suspect that designing for moving water is worse than accounting for wind in most respects.   

       As long as you account for that, I don't see anything wrong with this idea.
the porpoise, Sep 22 2014
  

       Welcome to the Halfbakery.
normzone, Sep 22 2014
  

       Indeed. Welcome, [sdk].
MaxwellBuchanan, Sep 22 2014
  

       (+) for vunnel.   

       Yes, yes, welcome!
the porpoise, Sep 22 2014
  

       WTAGIPBAN [+]
pertinax, Sep 23 2014
  

       + Hi there [sdk]. Nice idea. I'd like to see an elevator it the vunnel to get back up to the vertical ridge.
xandram, Sep 23 2014
  

       Good point about buoyancy cables.   

       I did some reading about deep ocean currents, and they are much slower than surface currents. Not sure how they behave in trenches, but the fluid forces may not be so bad.   

       What did you use to make such pretty calculations?
the porpoise, Sep 23 2014
  

       Where is this place that a trench is in the way of a tunnel?
bungston, Sep 23 2014
  

       Beaufort's Dyke, between Scotland and Ireland, is one such instance.   

       <link>
8th of 7, Sep 23 2014
  

       Oh the calculation where done in glorious MS Word hehe. (the equation editor in Word 2010/2013 is actually great)   

       About Beaufort's Dyke, that was exactly what made me think of this idea, I was reading the Wikipedia entry for Irish Sea fixed crossing.   

       If I have some more time maybe I'll look into the force of ocean currents seriously.
sdk16420, Sep 24 2014
  

       Since most tunnels are likely to be between two adjacent land masses with relatively shallow water in between, it's likely that tidal flows will be much more significant than currents per se.
8th of 7, Sep 24 2014
  

       I'd think you'd have more trouble with (and here is where I use made-up terms in place of proper ones I don't remember) the shearing activity that takes place between two layered volumes of different tempurature. Tides and currents are largely predictable things by comparison.
Alterother, Sep 25 2014
  

       Trains running on flat tracks fixed to solid ground develop troublesome oscillations at certain speeds andor certain track sections (braking into a curve at 15mph is the most common such scenario I've heard of). I can easily imagine this being dramatically worse when the track is an encapsulating non-rigid structure that can move about on three axes (rather than conventional tracks, which only shift in two planes, and not very much).   

       That problem may need to be addressed before we start looking deeply into external forces.
Alterother, Sep 26 2014
  

       A buoyant tube would have some advantages in areas of tectonic activity, if the mooring structure had the required resilience.
8th of 7, Sep 26 2014
  

       i dinged you because viaducts are bridges carrying lots of weight.   

       underwater you can easily solve the tranversing problem with a zipline for tension------and if the object being transported is very heavy you can solve it with either a hydrofoil lifting underwater wing&propulsion system, or simply with bouyancy control while the object is pushed or pulled along the length of the zipline.   

       a viaduct is entirely unnecessary just make it a zipline/single cable.
teslaberry, Sep 26 2014
  

       uh, [tesla], the poster is not suggesting an exposed submarine.   

       Since the structure would be securely anchored at the ends, and would be subjected to negligible vertical stress because of the bouyancy of the tube, your main remaining stress should be (mostly) horizontal hydrodynamic pressure. (Assuming we can neglect the weight of any vehicles passing through, which will probably be a bad assumption.)   

       As this is very similar to the one-sided hydrostatic pressure problem faced in building a concrete dam, I'd suggest solving it in the same way: arch it into the face of the force.   

       (With some added spoilers to compensate for any non- horizontal component of the current vector...)
lurch, Sep 28 2014
  

       One problem - many of the deep-sea trenches are trenches for a very tectonic reason.
MaxwellBuchanan, Jul 25 2016
  
      
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