Tunnelling through history: How Metro overcame odds in Old Delhi

New Delhi: From boring machines getting stuck during tunnelling work which stalled project timelines, to evacuation of people from some of the most densely-populated areas – the road to the Walled City was not easy for Delhi Metro Railway Corporation (DMRC), which surmounted these daunting challenges with innovation.

Interacting with reporters at the launch of 'Delhi Metro: Phase-III Challenges', a compilation of the engineering feats achieved and the challenges encountered during construction of Heritage Line, Magenta Line (Janak Puri West–Botanical Garden) and Pink Line (Majlis Park–Shiv Vihar), DMRC Managing Director Mangu Singh on Wednesday said that the Heritage Line – one of the shortest corridors (9.37 km) of the Phase-III network – turned out to be the "biggest challenge".

"During tunnelling work between Delhi Gate and Jama Masjid stations, and at Azadpur station (of Pink Line), tunnel boring machines (TBMs) got stuck due to various constraints.

"We had to use innovative techniques to overcome them, so as to avoid the delay in the project," Singh said.

DMRC Executive Director (Corporate Communications) Anuj Dayal, who authored the volume, said the Phase-III project was initially supposed to only span 103 km, but later got extended to 160 km

"Constructing Ashram station not only challenged the technical finesse of DMRC's architects, but also tested their experience and knowledge. Due to non-availability of land, which belonged to a private party and other constraints that come up during construction, the station box had to be redesigned and reduced considerably from 265 metres to 151," said Dayal.

Normally, a six-car train requires a space of 140 m on the platform.

However, due to space constraints, the platform length at Ashram station was reduced to 135 m.

Dayal added that DMRC architects and engineers, for the first time, completely redesigned the Ashram station, utilising all three levels to accommodate all the essential equipments, which are generally placed only at concourse and platform levels of underground stations.

In keeping with the constraints, an alternate design for the Ashram underground station was developed, and engineers were compelled to construct the station 20 m further below that what had been planned.

This was done so that a proposed underpass could be constructed above the station concourse level, Dayal said.

He added that engineers further had to design a tunnel ventilation system within the existing space and accommodate the air ventilation system at Ashram.

Tactfully, the tunnel ventilation system was accommodated at concourse and mezzanine levels. At either end, two TVFs were placed across the tracks; one over the other at concourse and mezzanine levels and were connected with each other.

"Apart from the tunneling work and platform design, the allocation of functional necessities, like auxiliary sub-station and environmental control system rooms are very crucial at the initial stage of construction," Dayal further said.