The Delhi Metro Rail Corporation (DMRC) has marked a significant milestone with a tunnel breakthrough at the Tughlakabad Railway Colony site on the Tughlakabad–Aerocity corridor, part of the Phase-4 expansion.

The 792-mtrs.-long tunnel was constructed using a 91-mtrs.-long tunnel boring machine (TBM) at an average depth of 18 mtrs. A total of 559 concrete rings were installed, each with an inner diameter of 5.8 mtrs. Civil works were carried out by Afcons Infrastructure. The breakthrough event was attended by Naveen Gulati, Member (Infrastructure), Railway Board, and senior DMRC officials.

Two parallel tunnels are being built between Tughlakabad and Tughlakabad Railway Colony stations for up and down train movement. The construction employed the earth pressure balancing method (EPBM), with precast segments cast at a mechanised facility in Mundka and steam-cured for early strength. The work took place beneath densely built-up areas, with ground movement monitored by sensors to ensure safety—DMRC confirmed no ground settlement occurred.

The Aerocity–Tughlakabad corridor includes 19.343 km of underground lines, part of the 40.109 km approved under Phase 4. DMRC continues to rely on TBMs to minimise surface disruption, a method used since Phase-1 and extensively in Phase-3.