A Delhi Metro build tunnel between two pillars
The tunnel is being built using a new technology-an Austrian tunneling method (NATM)-that excavates tunnels in tight spaces.
“The tunnel between Kalkaji Mandir and Okhla Phase III passes below piers 135 and 136 of the violet line. The distance between the two piers is 28m. It would have been impossible to construct twin tunnels within such a short space. Therefore, a decision was taken to construct a single tube twin tunnel using the NATM technology,” DMRC spokesman Anuj Dayal said.