TBMs Bhoomi and Srishti emerged at the same time at Pulbangash Metro Station last week, after digging 3km twin tunnels and the longest drive on Phase IV. The tunnels connect Derawal Nagar to Pulbangash on the Janakpuri West-R K Ashram corridor (Magenta line Extension).
During their 14-month journey, the TBMs made an average daily advance of 8.2m.
The tunnels were built at a depth of around 14-15m, passing through densely populated areas, including Rana Pratap Bagh and Punjabi Basti Colony. They also passed beneath the Najafgarh drain, a difficult section because of the uncertain structural condition of the drain. Despite tunnelling in submerged water, no damage was caused to existing structures.
The TBMs also had to bore through the under-construction Ghanta Ghar station as retrieving them at that location was not feasible.
The tunnels have an internal diameter of 5.8m and will be connected by six cross-passages.
This breakthrough follows another at the Chhatarpur Mandir site on the Delhi Aerocity-Tughlakabad Corridor on August 21.
