Kolkata's New Garia-Airport Metro project is set to include one of the sharpest curves in the country, a 568m curve at Chingrighata. This curve will navigate the space between Salt Lake Bypass and Eastern Metropolitan Bypass, passing over both the EM Bypass and the Chingrighata right-turn flyover. The viaduct, with a curve radius of 302m, will start from pier 310, located opposite Captain Bheri on EM Bypass, and end at pier 329, near Jal Vayu Vihar on Salt Lake Bypass.
The construction of this challenging section has been in the works for several years. In May 2023, Rail Vikas Nigam Ltd (RVNL), the company tasked with executing the 29km New Garia-Airport (Orange) Line, secured the Chingrighata site for the construction of Metro pillar 318, which is crucial for this curve. The process had been delayed for six years, with RVNL finally acquiring the site after extensive negotiations with the state administration.
Recently, girder-launching began, marking a significant step towards bridging the final 568m gap in the second phase of the Orange Line. Engineers are proceeding cautiously, given the complexity of constructing the viaduct, which overlaps with the Chingrighata flyover. The viaduct’s design allows it to circumnavigate the flyover, with the 19 spans ranging between 28m and 32m in length to form the curve. The viaduct will be 5.5m higher than the flyover, with around 100m of the curve extending inside the flyover’s carriageway. However, it is expected that the viaduct’s height will not obstruct vehicular traffic.
To build this section, the "balanced cantilever" method will be used, as heavy machinery will be required to hoist the precast concrete segments. The work is challenging due to the high volume of traffic at Chingrighata and the need for precision in construction.
This complex section is part of the New Garia-Airport Metro's broader efforts to connect key parts of Kolkata. The 8km Ruby-Sector V section is expected to be operational by March 2024. Currently, the corridor operates for 5.4km, from New Garia to Ruby.
In comparison, the East-West Metro’s underground section in Howrah also features sharp curves, including a 228m 'Kardashian' curve. Constructing this loop beneath the Brabourne Road flyover proved difficult due to the underground nature of the task and the limitations of tunnel boring machines (TBMs), which cannot exceed a 228m radius for curves.
As Kolkata's metro network continues to grow, this high-tech viaduct at Chingrighata serves as a testament to the city's commitment to improving its public transport infrastructure while overcoming engineering challenges.
