Impressively Wide Tunnels
Each of Doha Metro's tunnels is an enormous 6.7m in diameter.
During the rail network project, tunnel boring equipment originally excavated tunnels at a diameter of 7m. However, concrete tunnel rings, required to strengthen the tunnels, reduced their overall size to 6.7m/dia. Interestingly, it took 470,497 reinforced, pre-cast concrete segments to produce the 70,071 tunnel rings required to line 111km of tunnels.