By rosebell
As the first simultaneous twin tunnel breakthrough on Phase IV of the Delhi Metro rail project, the Delhi Metro Rail Corporation (DMRC) and Afcons have achieved this landmark.
Following excavation of 3km twin tunnels and the longest drive on Phase IV, in previous week TBMs Bhoomi and Srishti emerged at the same time at Pulbangash Metro Station, whereas the tunnels link Derawal Nagar to Pulbangash on the Janakpuri West-R K Ashram corridor (Magenta line Extension).
The average advance of TBMs over their 14-month journey was 8.2m per day.
Passing through densely populated areas, including Rana Pratap Bagh and Punjabi Basti Colony,the location of these tunnels were at a depth of almost 14-15m and they also passed beneath the Najafgarh drain, a difficult section because of the uncertain structural condition of the drain. Despite tunneling in submerged water, no damage was caused to existing structures.
Considering that retrieving these machine at that location was not feasible, they also had to bore through the under-construction Ghanta Ghar station.
While the tunnels have an internal diameter of 5.8m, the are due to be connected by six cross-passages.
On August 21, this breakthrough follows another at the Chhatarpur Mandir site on the Delhi Aerocity-Tughlakabad Corridor.
