In November 2022 the Delhi Metro Rail Corporation (DMRC) achieved a major construction milestone in Phase 4. They completed tunnelling work between Krishna Park Extension and Keshopur on the Janakpuri West – RK Ashram Marg corridor. A 73-m-long TBM EPB broke through at Krishna Park Extension after boring a 1.4-km long tunnel. Two parallel circular tunnels for up and down movement have now been constructed on this stretch, which is part of a 2.2-km-long underground section from Janakpuri West to Keshopur. The work on the other parallel tunnel on this section was completed in December 2021. Civil work on this particular underground section will be completed by early next year though the entire Janakpuri West – RK Ashram Marg corridor will not be ready until September, 2025.  

This new tunnel stretch is a continuation of the earlier Magenta line tunnel that was already constructed for the presently operational Botanical Garden – Janakpuri West corridor.

The tunnel - driven at a 14-16 m depth with an inner diameter of 5.8 m- has been lined with about 2,000 rings, composed of precast concrete segments produced at Mundka. These concrete segments were cured with a steam curing system to achieve more strength.

The tunnelling work involved innumerable challenges like the shifting of sewer lines at a depth of 8 m using the micro tunnelling method. In addition, due to heavy traffic on the Outer Ring Road, a subway was constructed using the box-pushing method without disturbing the traffic flow.

As part of the Phase 4 work approved so far, 28.76 kms of underground lines will be constructed. The Janakpuri West - RK Ashram Marg corridor will have underground sections of 9.41 km in total.

DMRC has been using TBMs for its tunnelling work since Phase 1, in Phase 3 about 50 km of underground sections were being built with 30 TBMs. For further information and to read more about the project please click here and in/11 for the tunnelbuilder archive and also visit http://www.delhimetrorail.com. 50/22.