To overcome engineering challenges in the ongoing Phase III projects, the Delhi Metro has resorted to the conventional method of tunnelling.
The DMRC usually applies the New Austrian Tunnelling Method (NATM), also known as Sequential Excavation Method (SEM), to carry out tunnelling work between Kalkaji Mandir and Okhla Phase III on the under-construction Janakpuri West-Botanical Garden corridor to pass below the currently operational Metro corridor.
Delhi Metro could not carry out the digging work using tunnel boring machines due to the foundation of the Metro viaducts and hence, it chose to adopt the conventional style for greater safety and cost efficiency. The tunnel passes below the Nehru Place-Kalkaji elevated section of the Mandi House-Badarpur Metro corridor.