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I don't think you can compare projects at this level of detail. My understanding of the Swiss tunnels (congratulations!) is that they were through hard rock wh

by mturmon 10y ago

I don't think you can compare projects at this level of detail. My understanding of the Swiss tunnels (congratulations!) is that they were through hard rock which provides predictable support for the tunnel. Tunnels in softer or less consistent materials have much less predictable costs, as do projects involving water.

m_mueller 10y ago
Tunneling through the alps isn't exactly easy, it's actually harder than through a normal sediment. Well, maybe cost wise a weak sediment may be more expensive (but not by a factor of 20x, more like 1.5-2x), but vertical rock formations bring all kinds of surprises, which leads to accidents including deaths, which leads to insurance premiums. To illustrate, here's a normal sediment: ----------------- 20y ----------------- 100y ---------------- .... here are the alps: | 10M years | 10.1M years | 12M years | .... Edit: You can also compare to the other link I posted in a sister comment, about a new tunnel through one of Zurich's hills. That project was actually less expensive per km than the Gotthard base tunnel, so I don't think the rock is the problem.