Naked Science Forum
Non Life Sciences => Technology => Topic started by: thedoc on 04/03/2016 14:50:01
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Preston asked the Naked Scientists:
Is it possible to build an underground railroad system to other countries or continents.
What do you think?
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I think the answer is probably no. The main reason would be tectonic plates. How do you build a tunnel through a break in the earth's crust made of molten lava, especially under miles of ocean? Even if it was technically possible, the incredible expense of overcoming the engineering challenges and the labor force required for construction would likely make it too expensive to execute.
For comparison, consider these excerpts from Wikipedia:
The Channel Tunnel (French: Le tunnel sous la Manche; also referred to as the Chunnel)[2][3] is a 50.5-kilometre (31.4 mi) rail tunnel linking Folkestone, Kent, in the United Kingdom, with Coquelles, Pas-de-Calais, near Calais in northern France, beneath the English Channel at the Strait of Dover. At its lowest point, it is 75 m (250 ft) deep.[4][5][6] At 37.9 kilometres (23.5 mi), the tunnel has the longest undersea portion of any tunnel in the world, although the Seikan Tunnel in Japan is both longer overall at 53.85 kilometres (33.46 mi) and deeper at 240 metres (790 ft) below sea level.
Surveying undertaken in the 20 years before construction confirmed earlier speculations that a tunnel could be bored through a chalk marl stratum. The chalk marl was conducive to tunnelling, with impermeability, ease of excavation and strength. On the English side the chalk marl ran along the entire length of the tunnel, but on the French a length of 5 kilometres (3 mi) had variable and difficult geology.
Tunnelling commenced in 1988, and the tunnel began operating in 1994.[35] In 1985 prices, the total construction cost was £4.650 billion (equivalent to £13 billion today), an 80% cost overrun. At the peak of construction 15,000 people were employed with daily expenditure over £3 million.[8] Ten workers, eight of them British, were killed during construction between 1987 and 1993, most in the first few months of boring.[36][37][38]
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In principle, yes, but in practice, why? The Channel Tunnel and similar ventures make economic sense when they span a short distance with a very heavy traffic demand. As the technology is mature, I guess that all those locations that meet the criteria already have a tunnel or a plan to build one. But once you are on dry land, and not trying to improve traffic flows within a city, it's a lot cheaper and easier to build surface railways, and for any distance exceeding 100 miles, airports make even better economic sense (no intervening infrastructure - just a mile of tarmac at each end!)
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Is it possible to build an underground railroad system to other countries or continents
It is possible, but not usually economic, because tunneling is expensive.
A 4km length of highway near my home was originally intended to be mounted on concrete piers. Due to complaints from locals, it was placed underground, which doubled the cost. And this was in rock that was geologically stable, and not very hard (sandstone).
Building a railroad on flat ground is even cheaper than an elevated railway.
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Their is one trans-continental rail tunnel contemplated between Asia and north America under the Bering strait, I look forward to its construction!