New Delhi: The DMRC today achieved a tunnel breakthrough of Delhi Metro’s Phase – III project at Naraina by completing the tunneling on the under construction Delhi Cantt – Narina Vihar- Mayapuri of the Majlis Park – shiv Vihar (Line-7) corridor. Dr. Mangu Singh, Managing Director/DMRC and other senior DMRC officials were also present during the event.
The Tunnel Boring Machine (TBM) emerged at Mayapuri retrival shaft site after making a 1.2 KM long tunnel from Delhi Cant. The tunneling on this stretch began on 2nd February 2015. The maximum depth of the tunnel is 22 meters below the earth’s surface.
This is another engineering landmark for DMRC as the TBM was dragged through the Naraina vihar station instead of retrieval it after installing 803 meters (578 rings) due to paucity of space for creating a shaft on the ground. The TBM was dragged about 210 meters and took about one month and was carried out by M/s J. Kumar-CRTG.
Generally, TBMs are retrieved through custom made retrieval shafts and then re-inserted through launching shafts in the new location. But such conventional engineering would have involved construction of separate retrieval and launching shafts, which would have required more land and displacement of properties above.
In addition, the process would have required a month each approximately for the retrieval and then the launching of the TBM. To avoid these hassles, the TBM shield was dragged using push ram cylinders.