Metro Railway Kolkata General Manager Subhransu Mishra on Saturday inaugurated the Purple Line tunnelling work by the second TBM (Tunnel Boring Machine), an official statement said.

A launching shaft measuring 37 m in length, 22 m in width, and 17 m in depth has been constructed inside the St Thomas School compound for this work, it said.

The work for one of the two tunnels commenced on July 10 by pressing into service TBM Durga.

Two TBMs — Durga and Divya — have been deployed to construct 2.65 km long twin tube tunnels from Kidderpore to Park Street, with Divya pressed into service from Saturday (October 11).

The 'breakthrough' by Durga and Divya is expected to be accomplished by December 2026 and March 2027 respectively, for the twin tunnels, the statement said.

Senior officials of Metro Railway, Rail Vikas Nigam Limited (RVNL) and St Thomas School representatives were also present on this occasion.

These new generation TBMs are safe and efficient and can bore at the rate of 80 mm/min, the statement said.

Each TBM, measuring 95 m in length and weighing about 600 tonne, is equipped with inflatable seals, pressure transducers, Precast concrete segments, 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 per cent completion of the top slab, while diaphragm wall (D-Wall) construction at Park Street station stands at 50 per cent.

A Metro official said that while presently trains are being run along the Joka-Majerhat corridor, the authorities were aiming to run services from Joka to Park Street in a few years' time.

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