New Delhi: Despite COVID related challenges, Indian Railways has achieved a major milestone by completing very difficult tunnelling work of 800m in Kolkata. The tunnelling work gets completed by Tunnel Boring Machine (TBM) in East West Metro Corridor with the breakthrough of "Urvi" at Bowbazar, Kolkata on May 15. With this breakthrough, the entire TBM tunnelling for the Kolkata East-West Metro Project is completed. The stretch was difficult for tunnelling work as it had century-old buildings. This challenging tunnel drive of 800m has been completed successfully amidst this pandemic situation following COVID-19 protocol.
The Tunnel Boring Machine 'Urvi' which had earlier completed the East Bound tunnel from Esplanade to Sealdah on October 9, 2020, was relaunched from Sealdah after necessary refurbishment and inspection on January 1, 2021, to complete the balance 800 m tunnelling work in West Bound tunnel from Sealdah to Bowbazar. This drive of tunnelling has been completed and the tunnel boring machine breakthrough at Retrieval Shaft at Bowbazar has been achieved on May 15.
This TBM (Urvi) has passed below Sealdah Flyover also for which vehicular movement on the Flyover was closed for three days for safety reasons. After completion of this TBM drive, the tunnel boring machine 'Urvi' along with the other stalled TBM 'Chandi' will be retrieved from this retrieval shaft at Bowbazar.
Excavation of shaft after ensuring the water-tightness of the shaft and the affected tunnel and retrieval of the TBMs are intricate activities that have to be done safely and hence will take time.
After completion of the entire excavation, both the TBMs will be retrieved in pieces from the shaft. The RCC flooring and roofing for the shaft area will be completed thereafter and the shaft top will be backfilled to prepare the ground for overground construction.
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