3 ms·

I assume so, but it's not all that clear to me why - if the tunneling vibrations are an issue, just dig deeper? The Gotthard base itself had massive problems wi

I assume so, but it's not all that clear to me why - if the tunneling vibrations are an issue, just dig deeper? The Gotthard base itself had massive problems with loose sediments - alpine sediments are vertical, so they change abruptly every few meters. You could also compare with the Durchmesser line in Zurich [1, 2, German]: ~2.1Bn USD, up from 1.9Bn projected at project start, 4.8km tunnel, 9.6km total length of new railway beneath, above and alongside urban housing, includes a new underground train station, 7 years to build from start to finish. You can also compare it to Tokyo. 5-10x cheaper to build their metro lines while their GDP per capita is only 37% less than the US. [1] https://de.wikipedia.org/wiki/Durchmesserlinie_Altstetten–Zürich_HB–Oerlikon https://de.wikipedia.org/wiki/Durchmesserlinie_Altstetten–Zü... [2] http://www.sbb.ch/content/dam/sbb/de/pdf/sbb-konzern/ueber-die-sbb/projekte/ausbau-schienennetz/DML_factsheet_weinbergtunnel_web.pdf http://www.sbb.ch/content/dam/sbb/de/pdf/sbb-konzern/ueber-d...

ubernostrum 10y ago
Digging under an existing city is hard. You have to thread your way through deep-driven building foundations, dodge or relocate underground pipes and cables, and maintain enough integrity to keep everything above from sinking while you do it. And (please don't take this the wrong way) a lot of places outside the US have been easier to build in because, over the past century, those places had to be completely rebuilt anyway following the massive devastation of two world wars. The US escaped that devastation on its own soil, but is paying an ironic price in that now it's difficult or even impossible to retrofit more modern infrastructure into our cities, because we still have all the old infrastructure that never got destroyed.
- kalleboo 10y ago
  Another example is the Malmö City Tunnel, drilled right under Sweden's third-largest city. $0.96 billion for 17 km (it even completed under time and under budget). Malmö as a city predates the European settlement of the United States, sustained no damage in WW2 and has many historical buildings. To be fair though, the geology in the area presents no special challenges.

ubernostrum 10y ago

Digging under an existing city is hard. You have to thread your way through deep-driven building foundations, dodge or relocate underground pipes and cables, and maintain enough integrity to keep everything above from sinking while you do it. And (please don't take this the wrong way) a lot of places outside the US have been easier to build in because, over the past century, those places had to be completely rebuilt anyway following the massive devastation of two world wars. The US escaped that devastation on its own soil, but is paying an ironic price in that now it's difficult or even impossible to retrofit more modern infrastructure into our cities, because we still have all the old infrastructure that never got destroyed.

kalleboo 10y ago
Another example is the Malmö City Tunnel, drilled right under Sweden's third-largest city. $0.96 billion for 17 km (it even completed under time and under budget). Malmö as a city predates the European settlement of the United States, sustained no damage in WW2 and has many historical buildings. To be fair though, the geology in the area presents no special challenges.