Metro gets set for longest run through Delhi’s belly

This month, the Delhi Metro will glide past yet another milestone as its line 2 stretches up to Qutab Minar. It is believed that the 24-km subterranean segment will be India’s longest underground tunnel for transport purposes.

Delhi Metro’s line 2 has, from the outset, held special challenges for the Delhi Metro Rail Corporation (DMRC) engineers because it had to connect areas that were highly populated. Numerous other factors made the construction of elevated rail tracks unfeasible.

The tunnel, from Central Secretariat to Qutab Minar, is a part of the second phase of Metro’s expansion and will cover a distance of 12.53-km. When operations commence, it will be connected to the existing underground stretch from Central Secretariat to Guru Tegh Bahadur Nagar which is also 12-km long. So residents of north Delhi, keen for a glimpse of the Qutab, can have a nonstop 24-km run through the Capital’s underbelly.

According to DMRC officials, finishing touches are being given to the structure and trial runs are already taking place.

The tunnel stretch from Central Secretariat to Qutab was constructed by using two different methods, revealed DMRC officials.

Eight German tunnel boring machines (TBM) were pressed into service to construct the structure from Central Secretariat to Saket. These huge machines drilled two parallel tunnels for the upcoming and downward trains for over two years. Officials said each of these TBMs was 30 metres long.

While the cutter head of the TBM is inserted into the ground, a part of the machine stays on the surface. These machines employ a technique that enables concrete slabs to be put in place to form walls even as the TBMs move on.

But even these monster machines could not be used on the Saket- to- Qutab route because the surface here turned out to be rockier than elsewhere.

Therefore, the Metro used the New Austrian Tunnelling Method (NATM) — where controlled blasts are used to move rocks and soil — on this stretch, the officials said.

To build the stations, DMRC opted for the conventional cover and cut technology in which the ground is dug from above. The C- Sec to Qutab stretch will have a total of eleven stations. These halts are scheduled at Central Secretariat, Udyog Bhavan, Race Course, Jor Bagh, INA, AIIMS, Green Park, Hauz Khas, Malviya Nagar, Saket and Qutab Minar.

The AIIMS station has been specially constructed to cater to the needs of patients headed for the institute as well as Safdarjung Hospital. Metro officials expect a daily ridership of 1.8 lakh passengers on this stretch daily.

The Delhi Metro’s Central Secretariat to Badarpur stretch will also have a 6.10- km underground stretch, while the Airport Express Link would have a 7.22- km tunnel.