Delhi Metro: Afcons Records Double TBM Breakthrough at Pulbangash

Afcons Infrastructure today celebrated a double breakthrough at Pulbangash Station of the Delhi Metro Magenta Line’s 7.46 km Derawal Nagar – RK Ashram extension.

This major milestone by tunnel boring machines (TBMs) Bhoomi (S-710) and Shristi (S-1134) was recorded after excavating 2996m & 2999m long tunnels from Derawal Nagar Station’s launch shaft. Both machines were launched one after the other in June & July 2023 for their first tunneling assignments in 85.86 km Delhi Metro’s Phase 4 and bored at an average rate of 8.2 meters per day.

Both Ø6.63m diameter Earth Pressure Balance (EPB) machines were manufactured by Herrenknecht and had passed factory acceptance tests after refurbishing in February 2023.

TBM S-710 was earlier deployed by Afcons in Chennai Metro’s Phase 1 (2015-2017) and at Ahmedabad Metro’s Phase 1 (2018-2020) where it was joined by S-1134 to work on Phase 1’s Package-1. Interestingly both machines had together recorded a historic final double breakthrough in Ahmedabad as well. 

Per DMRC’s press release, this is the “longest tunneling drive (almost 3 km) in Phase 4 works. The tunnels were built at a depth of around 14-15 metres below the ground, passing through densely populated areas, including Rana Pratap Bagh and Punjabi Basti Colony. They also passed beneath the Najafgarh drain, a sensitive section due to the uncertain structural condition of the drain. Despite tunnelling in submerged water conditions, no damage was caused to any 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 finish diameter of 5.8 metres, and a total of six cross passages are being constructed to connect the two tunnels for passenger safety.”

Delhi Metro Rail Corporation (DMRC) had awarded underground DC-05’s Rs. 2481.50 crore contract in January 2022 with a 42 month deadline.

7.46 km Package DC-05 will take 38.2 km Magenta Line deeper into North-Central Delhi, skirting Old Delhi, as part of the 28.92 km Janakpuri West – RK Ashram extension.

It’ll connect a ramp north of Derawal Nagar with RK Ashram via 6 stations at Derawal Nagar, Ghanta Ghar, Pulbangash (interchange with Red Line), Sadar Bazar, Nabi Karim & Ramakrishna Ashram Marg (interchange with Blue Line).

I’ve covered and written about 100+ TBM breakthroughs on my site and double breakthroughs are an extremely rare occurrence. This was the first one for Phase 4, but back in Phase 3 HCC-Samsung JV recorded one at Magenta Line’s Dabri Mor Station in 2014, while J Kumar-CRTG JV recorded one at Pink Line’s Vinobhapuri Station in 2016.

With this development, a total of 4 breakthroughs have been recorded on the 28.92 km Janakpuri West – RK Ashram extension of the Magenta Line. The other two were recorded by HCC – VCCL JV for Package DC-06 (Vikaspuri Shaft – Krishna Park Extension). They had deployed one Terratec tunnel boring machine (TBM) S86 “Triveni” which wrapped up tunneling works in November 2022.

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– TMRG