AMAR METRO
KOLKATA
PRESS RELEASE
TUNNELLING WORK OF PURPLE LINE STARTS AT KHIDDERPORE
Kolkata, Date: 10.07.2025
The tunnelling work of Purple Line from Khidderpore to Victoria has started today i.e. on 10.07.2025. Shri P. Uday Kumar Reddy, General Manager, Metro Railway, started this work this morning by pressing a button at St. Thomas School premises in Khidderpore in the august presence of his Excellency Consul General of Nepal, other senior officials of Metro Railway, Rail Vikas Nigam Ltd (RVNL), Defence Authority, CMRI Hospital, WBTC and St. Thomas School. Expressing his happiness, Shri Reddy has said “It is a historic day for the people of Kolkata as the Tunnel Boring Machine has started off. It is also a very important and joyous occasion for the people of Kolkata”.
The Tunnel Boring Machine Durga has started the tunnelling work towards Victoria today and 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, Khidderpore for this work. The 6.63 m diameter (outer) TBM has been assembled at Chennai and mobilized 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 Khidderpore to Park Street, beyond which tunnelling will be done by conventional Cut & Cover method. To cater 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, having length of 95 m and weighing approx. 600 tons 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 tunnel from Khidderpore to Victoria in the first phase having length 1.70 km and is expected to breakthrough at Victoria by May 2026.
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