Kolkata, July 10 -- Kolkata Metro on Friday achieved a major milestone in the construction of the Purple Line as Tunnel Boring Machine (TBM) Durga made a breakthrough at Victoria Metro Station, completing the first underground tunnel drive between Kidderpore and Victoria.
The breakthrough operation began at 10:10 am and concluded at 10:33 am after the TBM broke through the diaphragm wall, completing the 1.75-km tunnel drive.
Union Railway Minister Ashwini Vaishnaw hailed the achievement in posts on social media, sharing videos of the breakthrough and describing it as "engineering excellence beneath the city". "TBM Durga achieves breakthrough at Purple Line of Kolkata Metro. Congratulations to the team!" he wrote.
TBM Durga had begun tunnelling from a 17-metre-deep launching shaft at Kidderpore on July 10, 2025. During the year-long drive, it passed beneath one of the city's most technically challenging stretches, including heritage-sensitive zones, multi-storey buildings, several of them more than five decades old, and a canal.
Calling the breakthrough a major engineering milestone, Metro Railway General Manager Prem Sagar Gupta said: "In tunnelling projects, a breakthrough signifies the successful completion of a tunnel drive. We have completed 1,750 metres of tunnelling safely without any injury to workers."
Gupta said Metro Railway continuously monitored ground settlement through instruments installed along the alignment. "Our experts ensured that settlement did not exceed the permissible limit anywhere. Every millimetre of movement was monitored in real time," he said.
Metro services are currently operational on the elevated Joka-Majerhat section of the 14-km Joka-Esplanade corridor, while construction is continuing on the remaining elevated stretch to Mominpur and the underground section towards Esplanade.
The second running tunnel is being excavated by TBM Divya, which was launched from the same shaft at Kidderpore in October 2025. Gupta said the machine is expected to reach Victoria by the end of August, completing both running tunnels between Kidderpore and Victoria.
TBM Durga will now be dismantled and lifted out for maintenance before being relaunched for the 900-metre tunnel drive between Victoria and Park Street. The remaining underground stretch between Park Street and Esplanade will be constructed using the cut-and-cover method.
Gupta said Metro Railway was targeting completion of the Purple Line up to Esplanade by December 2029. He said the project was progressing with the support of the state government and local authorities and expressed confidence that the deadline would be met.
Also on the cards are extensions of the Purple Line to Diamond Park via IIM-Calcutta in the south, and to Eden Gardens in the north. Land acquisition has already begun for both stretches. Once completed, the 1.7-km southern extension and the 1.6-km northern extension will take the corridor's length to about 18 km.
Published by HT Digital Content Services with permission from Millennium Post.