h a l f b a k e r yWe have a low common denominator: 2
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Tunnels are very useful. Unfortunately, they are also very costly, especially if you aren't willing to tell people they can't use streets whilst you dig a trench in them and have to use more expensive methods that dig one out from underground.
The problem, as far as I can tell, is that soil has a
tendency to fall on you if you dig out the soil beneath it. This necessitates the installation of a supporting roof, which has to be installed as you dig to keep the tunnel open.
But! Many of the tunnels we wish to dig run through clay subsoils. Clay is famously the material bricks are produced from, through the application of heat. If we could fire this clay insitu, we could create a tunnel *before* digging it out.
My proposal: to poke (or potentially pull, once a guide wire is in place) steel wires/rods through it to form an archway pattern, which will then be electrically heated. This will cause the clay around the wires to harden and sinter into a strong arched tunnel, which can then be dug out without worrying about a collapse. The temperatures required to achieve this are comfortably below the melting point of steel, allowing us to use cheap metal heating elements.
Once the tunnel is excavated, we would then likely install a more permanent structure and backfill rather than relying on the long term stability of the insitu clay. The cheap tunnels thus produced can then be used for railways, utilities, roads, and lairs.
Tunnelling and mining with microwaves
https://www.allplan...ng-with-microwaves/
In the context of breaking through rock rather than sintering it, but it suggests energy can be directed where we need the heat. Microwaves could also reach far higher temperatures, allowing us to produce tunnels of glass. [Selky, Nov 04 2024]
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This will only work for tunnels with large sections that are entirely clay, and it will cost almost as much to make 20 little tunnels as 1 big one. [+] for innovation even though the idea won't work. |
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This is absolutely fascinating and I have absolutely no idea if it would work. Enthusiastic [+]. |
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Might look into just putting pipes in and blasting then with natural gas. Could even to one section at a time. |
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Now if you're doing an arch, we know that structurally those have been holding up for thousands of years, doing this to at least prep for a concrete / rebar reenforced tunnel could be friggin' genius. |
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I'm not sure doing it FIRST would work (but it is a neat concept).
But doing it "as you go" with a TBM (instead of installing concrete segments) could be a lot more feasible; you could just heat up the rim of the TBM shield. Apart from the "only works in clay" problem as [Voice] pointed out. |
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[voice], [neutrinos _shadow], |
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It may work in other soils, given sufficient heat. Might need graphite electrodes though to sinter sand. Or microwaves, we could imagine a tunnelling system that uses microwaves to sinter the walls a metre ahead of itself before excavating, then another metre, then another... |
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You could inject ferrous material in geometric shapes and then wait for a thunderstorm to direct lightning to your pre-built rods creating fulgurite glass ribs. |
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Some judiciously placed re-bar and Thor's yer uncle. |
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