Norway Is Building The World's First 'Floating' Underwater Tunnels (thenextweb.com)

An anonymous reader writes from a report via The Next Web: Norway plans to build "submerged floating bridges" to allow drivers to cross its bodies of water. The Next Web reports: "The 'submerged floating bridges' would consist of large tubes suspended by pontoon-like support structures 100 feet below water. Each will be wide enough for two lanes of traffic, and the floating structures should ease the congestion on numerous ferries currently required to get commuters from Point A to Point B. Each support pontoon would then be secured to a truss or bolted to the bedrock below to keep things stable." A trip from Kristiansand to Trondheim is roughly 680 miles and could take as long as 21 hours due to the seven ferry trips required along the way. While building normal bridges would cost significantly less than the $25 billion in funds required for the tunnel project, the fjords and difficult terrain make them unsuitable candidates. The pricey tunnel project could cut the trip time to just 10 hours when it's expected to be finished in 2035.

Comments

San Francisco's Transbay Tube

[Hadlock]

San Francisco's Transbay Tube does this. It's a bunch of segments bolted together, and then it was weighted down with thousands of pounds of granite fill/gravel and they pumped all the water out of it. The bottom of the San Francisco bay is pretty flat and muddy compared to Norway, I suspect, so they just let it sit on the bottom, rather than precariously suspend it in the water(?!?)
 
  https://en.wikipedia.org/wiki/Transbay_Tube