ITD-ITD Cementation India Ltd. JV on Saturday night celebrated the completion of tunneling work for Kolkata Metro’s 16.34 km east-west Line-2 which will connect Howrah Maidan with Sector V.
This historic final breakthrough, not visible to workers, was accomplished by Tunnel Boring Machine S-616 (Urvi) at Bowbazar’s mid-shaft where excavation is ongoing. For its final assignment, the Ø6.65m Herrenknecht EPB machine traveled approximately 800 meters in 4.5 months since it was relaunched in January from Sealdah Station.
This was TBM Urvi’s fifth breakthrough in Kolkata, 5.5 km Package UG-2’s 8th breakthrough for the Esplanade – Subhash Sarovar Ramp section, and overall Line-2’s 14th breakthrough.
Similar ‘hidden’ TBM breakthroughs have been performed by Afcons Infrastructure at Chennai Metro’s Sir Theagaraya College Station (By S-711 and 219-364) as well as locally in Kolkata by TBM S-639 at Howrah Station and Mahakaran Station.
It took a little over 9 years for this event to be recorded since tunneling started on February 25, 2012.
Urvi and its sister machine Chandi (S-615) had first built the tunnels between the Subhash Sarovar Ramp – Phoolbagan Station – Sealdah in 2012-2013. A realignment of the line in central Kolkata forced the firm to halt further tunneling for over 5 years during which both TBMs were sent to work on Delhi Metro’s Magenta Line tunnels, and then brought back to Kolkata to finish the pending tunnels.
TBM Chandi commenced its final journey from Esplanade to Sealdah on January 25, 2019 for building the west-bound down-line tunnel, and TBM Urvi started its journey on February 15 for the east-bound up-line tunnel – both roughly 2.45 km long.
Tunneling work came to an abrupt halt on August 31, 2019 when Chandi hit an aquifer leading to heavy soil displacement in the Bowbazar area. This triggered the collapse of several residential buildings and necessitated the construction of a 22m deep 40m x 15m “emergency” midshaft on the west-bound tunnel to retrieve both machines.
Urvi resumed tunneling on February 2020 after Kolkata’s High Court allowed work to restart under strict supervision, made its penultimate breakthrough at Sealdah in October 2020, was extensively refurbished, turned around, and relaunched for building the remaining 553 rings (approx. 800m) west-bound tunnel towards Bowbazar.
With tunneling works now completed, workers will now focus on excavating the midshaft and prevent water from entering it in the future. Parts of Chandi (facing east towards Sealdah) will first be pulled out followed by Urvi (facing west towards Esplanade). After both machines’ parts are removed, the base slab RCC flooring and roof work will be completed, and soil will be backfilled.
While the 2.1 km Phoolbagan – Sealdah section could possibly open for commercial operations in mid-2022, I see the rest of the line (Sealdah – Howrah Maidan) opening up no sooner than mid-2023 with the quantum of pending systems, architectural finishing, testing and other activities to go.
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