The Delhi Metro Rail Corporation (DMRC) has announced that it has reached a significant construction milestone in the ongoing Phase 4 of the Delhi Metro. In a statement released today, the DMRC revealed that it has successfully completed an underground tunnel connecting Chhatarpur and Chhatarpur Mandir Station on the Tughlakabad-Aerocity corridor. According to the DMRC, a Tunnel Boring Machine (TBM) broke through at Chhatarpur Mandir Station this morning after boring an 860-meter-long tunnel. The breakthrough was achieved using a 97-meter-long TBM. Two parallel circular tunnels have been constructed to facilitate up and down movement along the Aerocity-Tughlakabad corridor, with the breakthrough for the second tunnel having been completed on August 21, 2024. The new tunnel is situated approximately 12 meters deep and has 613 rings installed within it, boasting an inner diameter of 5.8 meters. As part of the Phase 4 construction, 40.109 km of underground lines are being laid, with this particular corridor measuring 19.343 km. The DMRC noted that the tunneling work encountered several challenges, including the need to shift a 66 kV electrical HT line. Additionally, the TBM successfully crossed beneath the Yellow Line viaduct without disrupting operations on the existing line. TBMs are particularly effective for underground tunneling in densely populated urban areas, and the DMRC has been employing them since Phase 1. During Phase 3, approximately 50 km of underground sections were constructed using around 30 TBMs throughout the national capital.