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  1. None of those is an example of something with a vehicle running across it, e.g. an example for mastering the vibrations of the elastic structure in practice. (I don't say it's impossible, just untested.)

  2. I don't think the tunnel would be buoyant all by its own displacement. The typical cross section of a single-track tunnel is somewhat less (c. 50 m³), but the per metre displaced water is still an order of magnitude above the per metre weight of an European train (I think you can get as high as 100 tons for 10 metres = 10 t/m in Britain [25t axleload self-emptying car for mined stuff]). However, I would estimate the tunnel walls to be much heavier. for example, the immersed tube of the Marmaray Tunnel comes in at 140 tons per metre (or 70 tons per track), and a 'double-hull', buoyed tunnel with two tubes for high-speed tracks should be heavier than that.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Tue Dec 22nd, 2009 at 06:13:17 PM EST
[ Parent ]
  1. I imagine there are plenty of vibrations in km tall drilling platforms.

  2. But the Marmaray is meant to sink!  As I suggested to JakeS, his (indirect) suggestion of ferrocement is very appealing, given its lightweight, toughness, and proven record with maritime applications.  There are 100 year old boats still floating in the sea.  AAC (aerated concrete) with a ferrocement outer would be even better, given its positive natural buoyancy.  We know that positive buoyancy is possible, given that there are ships that carry trains.  It's then just a question of diameter and materials choice.
by njh on Tue Dec 22nd, 2009 at 06:34:08 PM EST
[ Parent ]
But the Marmaray is meant to sink!

Actually, it is meant to float: before the interior is completed, just at the limit of buoyancy so that it can be towed into the right position before it is sunk to its place. Buoyancy doesn't matter once it is at the bottom and covered over.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Tue Dec 22nd, 2009 at 06:49:56 PM EST
[ Parent ]
1) And in skycarpers and radio towers and suspension bridges and cable-stayed bridges too. But the typical vibrations and the critical components in all of these are different and need to be tested.

Ferrocement, and/or larger tube diameter for buoyancy, now that I don't see why it can't work. You should patent it :-)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Tue Dec 22nd, 2009 at 06:57:31 PM EST
[ Parent ]

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