Purple Line progress: TBM starts digging from Kidderpore
The Statesman | 11 July 2025
In a major relief to the residents of Kidderpore, the tunnelling work of Purple Line from Kidderpore to Victoria started today. The TBM, Durga will burrow the tunnel from Kidderpore to Victoria in the first phase and is expected to break through at Victoria by May 2026.
The tunnelling work started ceremonially this morning with Mr P Uday Kumar Reddy, general manager of Metro Railway, giving a green signal to the work by pressing a button at St. Thomas School premises in Khidderpore in the presence of consul general of Nepal, other senior officials of Metro Railway, Rail Vikas Nigam Ltd (RVNL), defence authority, WBTC and St. Thomas School.
Expressing happiness, Mr Reddy said: “It is a historic day for the people of Kolkata as the tunnel boring machine has started. It is also a very important and joyous occasion for the people of Kolkata.”
The tunnel boring machine, Durga started the tunnelling work towards Victoria today and is expected to complete the tunnelling work till Park Street at the end of 2026.The launching shaft having size 37 m length x 22 m wide x 17 m deep has been constructed inside the St. Thomas School, for this work. The 6.63 m diameter (outer) TBM has been assembled at Chennai and mobilised to Kolkata in the month of March, 2025 for subsequent assembling and lowering. Two TBMs (Durga and Divya) are being used for the construction of twin tube tunnels from Kidderpore to Park Street, beyond which tunnelling will be done by conventional ‘Cut and Cover method.’
To cater to the effects of high ground water table and soft soil condition in the city of Kolkata, earth pressure balancing (EPB) type TBMs are being used to construct the bored tunnels.
The TBMs, according to the city Metro office, having length of 95m and weighing approx. 600 tonnes are equipped with inflatable seal, pressure transducers tail skin grease (TSG) lines and backup TSG pump as an additional precaution considering the soil strata of Kolkata. Precast concrete segments of M50 Grade having thickness 275 mm are being used to achieve a finished tunnel having 5.80 m diameter.
The TBM, Durga will bore a tunnel from Kidderpore to Victoria having length 1.70 km.