Tunnel over tunnel, an engineering wonder of DMRC engineers

New Delhi: DMRC has achieved several milestones while completing its phase-3 project. While constructing the Hauz Khas Metro station, the Delhi metro has turned one of the major obstructions into an engineering wonder by creating a network of crisscross underground tunnels. According to an official, construction of the Hauz Khas station was a massive challenge for the Delhi Metro team. Since it was an interchange facility, the engineers also had to ensure that the inter connectivity between the old and the new portion of the Hauz Khas station was seamless and comfortable.

Along with the interchange station, the underground corridor of the Janakpuri West-Botanical Garden line also crisscrossed with the already operational yellow line of the Delhi Metro network at Hauz Khas. Therefore, the tunnels of the new line are also passing below those of functional line. However, the present station of Hauz Khas is 17-metre deep. For the construction of the new station, it was not possible to go below the existing station, as the foundation of a nearby flyover is 32-meter deep. So, the option left was to go deeper with 42-meter deep foundation, which was a very difficult task. So, the new metro tunnel at Hauz Khas was decided to be built just 29-meter deep at a point just after the station. "We have passed three meters below the existing tunnel. Proper measures were taken to prevent any movement of the existing tunnel. Settlement chances were prevented through grouting. D-wall was constructed around the existing tunnel to provide support while the new tunnel was being created," official said.

The official further added that, in phase-2 tunnel of the Airport Express line had passed below the two-tier Rajiv Chowk Metro station at a depth of about 45-meter. However, such a feat had never ever been achieved in Delhi Metro in its first two phases. In Phase-3, apart from Hauz Khas, tunnel have been constructed below operational tunnels at three locations.