TBM Divya and Durga begin Tunnelling for Kolkata Metro Purple Line

Kolkata, India (Metro Rail Today): Kolkata Metro’s ambitious Purple Line (Joka–Esplanade Corridor) project achieved another major milestone today with the formal commencement of tunnelling by the second Tunnel Boring Machine (TBM) ‘Divya’ from Khidderpore to Victoria. The breakthrough event was inaugurated by Shri Subhransu Mishra, General Manager, Metro Railway, at the St. Thomas School premises, marking a new chapter in the expansion of the city’s underground metro network.

Senior officials from Metro Railway, Rail Vikas Nigam Limited (RVNL), and St. Thomas School were present at the ceremony. The event follows the start of tunnelling work on July 10, 2025, when the first TBM, ‘Durga,’ began excavation on the same stretch.

A launching shaft, measuring 37 meters in length, 22 meters in width, and 17 meters in depth, has been constructed within the St. Thomas School compound for the deployment of TBM ‘Divya’.

The 6.63-meter diameter TBM, manufactured and assembled in Chennai, was transported to Kolkata in March 2025 for assembly and lowering operations. The two advanced TBMs — ‘Durga’ and ‘Divya’ — are being used to construct 2.65 km-long twin tunnels from Khidderpore to Park Street, one of the most technically challenging segments of the Purple Line.

The breakthroughs are expected by December 2026 (TBM Durga) and March 2027 (TBM Divya), respectively.

Each TBM measures 95 meters in length and weighs around 600 tons. Designed for precision and safety, the machines can bore at a speed of 80 mm per minute, ensuring minimal ground disturbance in the dense urban environment.

Equipped with inflatable seals, pressure transducers, Tail Skin Grease (TSG) lines, and backup TSG pumps, the TBMs are optimized to handle Kolkata’s complex subsoil conditions.

The tunnels are being lined with M50-grade precast concrete segments, each 275 mm thick, providing an inner diameter of 5.80 meters for the finished tunnel.

Significant civil progress has been recorded along the alignment:

• Victoria Station: 66% completion of top slab achieved.

• Park Street Station: 50% completion of diaphragm wall (D-Wall) construction.

The underground section from Mominpur to Esplanade will be one of the most vital parts of the Purple Line, improving city-wide connectivity and easing surface congestion.

“The commencement of TBM ‘Divya’s’ tunnelling marks another milestone in Kolkata’s urban transformation journey,” said Mrs. Mamta Shah, MD & CEO, Urban Infra Group.
“Metro projects like the Purple Line demonstrate India’s growing expertise in complex underground construction. The deployment of modern TBMs under dense city zones like Khidderpore and Victoria showcases the engineering precision and sustainability goals driving India’s next-generation metro infrastructure.”

The Joka–Esplanade (Purple Line) is designed to enhance connectivity between the southern and central parts of the city. Once complete, it will ease congestion, reduce vehicular emissions, and offer a faster, more comfortable mode of urban transport.

With two TBMs operating simultaneously, Metro Railway Kolkata and RVNL are on track to deliver one of India’s most advanced underground metro corridors, setting new benchmarks in safety, sustainability, and project execution.