However, building passenger transit in an urban area is a very different thing, even if a long underground tunnel is a challenge in itself.
Mining through solid rock is not really that expensive these days. But when building metropolitan transit, arranging traffic around of an existing population is not easy, and building transit stations is an expensive business.
Making a tunnel through solid, hard rock is in any case cheaper than making a tunnel through non-solid earth which needs to be supported for every inch all the time.
Regarding cost of mining solid rock: in fact, where I live, I think in the construction of underground train line, the actual cost of mining is pretty much offset by the price for sale of rock matter, which is then used for claiming land from sea to construct new housing. It is fairly silly over here because we have a low population and lots of land, but when the city claims new land, it can build there and sell it without purchasing it from existing owners, and all the increase in land value from zero (in fact no land at all) goes to the pockets of the city, and the pockets that the city chooses.
> Regarding cost of mining solid rock: in fact, where I live, I think in the construction of underground train line, the actual cost of mining is pretty much offset by the price for sale of rock matter
Really? The Cross rail project in London cost only 2bn more than the Swiss project but does exactly that, create an entirely new line under the whole of London, which is ridiculously hard to dig under (or so I've heard). Why the hell does it cost $50bn for you?
Cross-rail runs mostly on existing lines. Only 13 miles of the 85 total are new tunnels, so cost per mile is still almost a billion dollars.
(Being a bit unfair here, because the tunnelling cost is probably less than half the cost - the other half being rebuilding half a dozen massive underground train stations while keeping them operational.)
Where did you read that? The project site says they have created 26 miles of new tunnels, also wider ones than ever before (6.2m). As well as 10 new stations. And all of this is slap bang in the middle of Europe's biggest city, which is pretty damn poorly laid out and not exactly conducive to huge scale construction projects.
True, but it's not like building a dual carriageway where it's essentially one road split in two, it's two independent tunnels running mostly in parallel. I'd wager that's more than twice as hard to do.
Mining through solid rock is not really that expensive these days. But when building metropolitan transit, arranging traffic around of an existing population is not easy, and building transit stations is an expensive business.
Making a tunnel through solid, hard rock is in any case cheaper than making a tunnel through non-solid earth which needs to be supported for every inch all the time.
Regarding cost of mining solid rock: in fact, where I live, I think in the construction of underground train line, the actual cost of mining is pretty much offset by the price for sale of rock matter, which is then used for claiming land from sea to construct new housing. It is fairly silly over here because we have a low population and lots of land, but when the city claims new land, it can build there and sell it without purchasing it from existing owners, and all the increase in land value from zero (in fact no land at all) goes to the pockets of the city, and the pockets that the city chooses.