This is one of the six boring heads that carved the hard rock sections (~80%) of the Gotthard tunnels 2002--2007 (so-so youtube documentary about the Gotthard Tunnels project) |
Now I know why I was so hot inside the Gotthard tunnel when I drove through it back in 2016. The rock itself is as warm as 46°C |
a common structural element in Europe is the steel mesh box full of rocks. On Krk island in Croatia, I saw a whole house made this way. Sorry I didn't get a picture of that. |