SECOND TUNNELLING WORK OF PURPLE LINE STARTS AT KHIDDERPORE
Kolkata, Date: 11.10.2025
The tunnelling work of the Purple Line from Khidderpore to Victoria had commenced earlier on 10.07.2025. Today, i.e. on 11.10.2025, Shri Subhransu Mishra, General Manager, Metro Railway, inaugurated the tunneling boring work by the second Tunnel Boring Machine (TBM) Divya at St. Thomas School premises, Khidderpore. Senior officials of Metro Railway, Rail Vikas Nigam Limited (RVNL), and St. Thomas School were also present on this occasion.
A launching shaft measuring 37 m in length, 22 m in width, and 17 m in depth has been constructed inside St. Thomas School for this work. The 6.63 m diameter (outer) TBM was assembled in Chennai and moved to Kolkata in March 2025 for assembling and lowering operations.
Two TBMs — Durga and Divya are deployed to construct 2.65 km long twin tube tunnels from Khidderpore to Park Street. breakthrough is expected by December 2026 and March 2027, respectively.
These new generation TBMs are safe and efficient and can bore at the rate of 80 mm/min. Each TBM, measuring 95 m in length and weighing about 600 tons, is equipped with inflatable seals, pressure transducers, Tail Skin Grease (TSG) lines, and backup TSG pumps as additional safety measures suited to local geological conditions. Precast concrete segments of M50 grade, with 275 mm thickness, are being used to construct the finished tunnel with an inner diameter of 5.80 m.
At present, Victoria station construction work has achieved 66% completion of the Top Slab, while Diaphragm Wall (D-Wall) construction at Park Street station stands at 50% completion.
