NEW DELHI: The DMRC is developing over 40 km of new underground corridors as part of its Phase 4 expansion, which constitutes about 50% of the total lines being developed across five different corridors, according to a senior DMRC official.
It is constructing 27 underground stations in Phase 4. The DMRC has already completed a small underground section from Janakpuri West to Krishna Park of about 2 km. This is an extension of the Magenta Line, the officer said.
This is a major engineering feat since the underground corridors are passing through a variety of strata such as crowded residential and commercial areas in Sadar Bazar, Ajmal Khan Park, etc., he said.
Generally, DMRC constructs the underground metro stations using conventional cut-and-cover technology while the tunnels are built with the help of tunnel boring machines (TBM), the officer said.
However, a small section on the Aerocity-Tughlakabad corridor near Tughlakabad was built using the NATM technology (New Austrian Tunnelling Method). This method of tunnelling has also been used earlier by the DMRC with great success, the officer said. TBMs are especially useful for underground tunnelling work in congested urban areas. The DMRC has been using TBMs for its tunnelling work since Phase 1.
“While the Aerocity-Tughalakabad corridor will have about 19 km of underground corridor, the Janakpuri West-RK Ashram Marg corridor will have about 9 km of underground sections. The Inderlok-Indraprastha corridor will have over 11 km of underground lines. The Majlis Park - Maujpur and the Lajpat Nagar-Saket G Block sections will not have any underground stations,” the official shared.