Simultaneous breakthrough on DMRC Phase IV

The Delhi Metro Rail Corporation (DMRC) and contractor for the civil package M/s Afcons have successfully completed the first simultaneous twin tunnel breakthrough of twin TBMs on Phase IV of its underground Metro construction works. The Twin Tunnel drive span is approx. 3 km and is DMRC’s longest on the Metro Phase-IV works.

The two TBMs, Bhoomi and Srishti, emerged concurrently at Pulbangash Metro Station, marking the completion of tunnels connecting Derawal Nagar to Pulbangash on the Janakpuri West – R K Ashram corridor (Magenta line Extension). The event was graced by the presence attended by MD, DMRC.

This is one of those rare occasions when two TBMs have emerged simultaneously after boring parallel tunnels. It is a major tunnelling feat as the engineers had to meticulously monitor the movement of the two parallel machines.

Both TBMs were successfully retrieved at Pulbangash Metro Station after just over 14 months, covering a length of approx. 2997m, at an average rate of 8.2m per tunnel per day. The tunnels were built at a depth of around 14-15m below the ground, passing through densely populated areas, including Rana Pratap Bagh and Punjabi Basti Colony. They also passed beneath the Najafgarh drain, a sensitive section of the drive due to the uncertain structural condition of the drain. Despite tunnelling in submerged water conditions, no damage was caused to any of the existing structures. The TBMs also had to bore through the under construction Ghanta Ghar station as retrieving them at that location was deemed unfeasible.

The tunnels have an internal finish diameter of 5.8m, and a total of six cross passages are now being constructed to connect the two tunnels for passenger safety.

This breakthrough follows another major achievement on 21^st August, 2024, when DMRC completed a TBM breakthrough at the Chhatarpur Mandir site on the Delhi Aerocity- Tughlakabad Corridor.

With this twin tunnel breakthrough at Pulbangash, DMRC has built on the success of its earlier tunnelling achievements. The tunnelling work on this stretch began with the deployment of TBM Bhoomi on 18^th June 2023, followed by Srishti on 19^th August 2023.