The Delhi Metro Rail Corporation (DMRC) is making significant progress on Phase-IV of the metro network. This phase comprises a total of 65 km, of which 28 km will be underground. The DMRC has already constructed a 2.2 km tunnel between Krishna Park Extension and Keshavpur on the Janakpuri West-RK Ashram Marg corridor, while work is ongoing on the 1.27 km tunnel between Chhatarpur and Kishangarh stations on the Aerocity-Tughlakabad corridor. In the coming months, tunneling will commence on several other stretches. The underground stations are being constructed using the traditional 'cut and cover' technology, but special Tunnel Boring Machines (TBMs) are being employed for the tunnels.
Due to the routes' passage through heavily populated areas, the DMRC faces a substantial hurdle in completing the 18 stations it plans to construct on the underground portion of Phase-IV. Throughout the underground work, the structures above the work zones will be continuously observed. A total of 19 km of the line's total length will be buried along the Aerocity–Tughlakabad corridor, while 9 km will be subterranean along the Janakpuri West–RK Ashram Marg sector. By the end of 2025, the DMRC hopes to have finished the full Phase-IV project.
DMRC officials have stated that tunneling work will commence soon on several stretches, including Sangam Vihar-Anandamayi on the Aerocity-Tughlakabad corridor, and Derawal Nagar-Pul Bangash and Nabi Karib-Pul Bangash on the Janakpuri West-RK Ashram Marg corridor. The tunneling work will be monitored, and the buildings above the tunnels will be regularly checked. The use of TBMs is revolutionizing tunneling work worldwide, according to a DMRC official, as they do not affect surrounding buildings or other structures on the ground while making the tunnels.
TBMs are incredibly useful in underground tunneling work in congested urban areas, and the DMRC has been using them since Phase-I of the project. During Phase-III, when the 50 km underground section was constructed, approximately 30 TBMs were employed in Delhi. The Janakpuri West-RK Ashram corridor (Magenta Line) will have 22 stations, 11 of which will be underground. The Tughlakabad-Delhi Aerocity (Silver Line) will have 15 stations, seven of which will be underground. Finally, the Majlis Park-Maujpur (Pink Line) will have eight stations.
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