Unveiling Success Story of India's First Underwater Metro Rail Project in Kolkata

MRT Online Desk Posted on: 2024-03-07 17:10:00 Viewer: 728 Comments: 0 Country: India City: Kolkata

Unveiling Success Story of India's First Underwater Metro Rail Project in Kolkata

In a historic moment, India proudly inaugurated its first-ever underwater metro project, marking a significant leap in the realm of transportation. The 45-second underwater tunnel connecting Kolkata with its twin city, Howrah, is set to revolutionize commuting, slashing the travel time from 90 minutes by road to a mere 40 minutes. Let's dive into the captivating journey of how Kolkata created history with this groundbreaking infrastructure.

The Genesis of Kolkata's Metro Saga

Kolkata and Howrah, bustling with trade and factories, faced a perpetual challenge – congested public transport. The iconic Howrah Bridge, though a marvel, couldn't alleviate the transportation woes. Recognizing the urgency, Dr. B.C. Roy, the Chief Minister of West Bengal in 1949, championed the idea of an underground railway. Thus, the Kolkata Metro was born in 1984, evolving from a 3.4 km track with five stations to a sprawling 31.4 km network with 26 stations, half of which runs underground.

A Century-Old Vision Resurrected

Interestingly, the concept of an underwater metro in Kolkata dates back to 1921. British engineer Harley Dalrymple-Hay envisioned a 10.6 km underground railway with a tunnel beneath the Hooghly River, connecting Kolkata and Howrah. Despite his grand plan, insufficient funding and doubts about the city's soil properties halted the project. Fast forward to the present, the underwater stretch of the metro boasts twin tunnels under the Hooghly River, spanning 520 meters.

Unveiling the Engineering Feat

Executing the underwater metro project required meticulous planning and groundbreaking engineering. The project involved excavating over 5,400 meters of the tunnel, employing two tunnel boring machines (TBMs) named Rachna and Prerna. These colossal machines, reminiscent of those used in London's cross rail project, dug through the earth, creating a path for progress.

The tunneling operation faced unique challenges, with TBMs navigating soft clay strata at a lesser depth over structures almost a century old. Mining below Howrah Railway Yard, one of the busiest railway yards in the country, with over 670 running trains and a daily footfall of 10.5 lakh, posed a significant challenge, requiring mining over 350 meters below the yard for each tunnel.

TBMs had to negotiate a sharp curve of radius 228 meters, plunging into new geology characterized by stiff clay. Obtaining CRS (Commission of Railway Safety) approvals for the project proved to be another gigantic task, achieved only after the satisfactory closure of all requirements.

Key innovations were introduced, such as recruiting a highly experienced tunnel crew, enabling TBMs to shut down like a submarine in the remote possibility of river water ingress for safe evacuation. Afcons designed a 'soft eye' of Styrofoam, replacing M-40 concrete, which proved extremely effective for the project.

A Journey Marked by Setbacks

The underwater metro project, initially slated for completion in 2014, faced multiple setbacks. Realignment caused a pause from 2012 to 2015, and in August 2019, a tunnel boring equipment mishap struck an aquifer, resulting in earth subsidence and building collapses. The densely populated Bowbazar area experienced land subsidence, causing houses to crumble like a pack of cards. Despite these challenges, the project finally reached fruition in April last year, with trial runs paving the way for today's momentous inauguration by the Prime Minister's Office.

Key Innovations, Challenges, and Relief Measures

The engineering marvel of Kolkata's underwater metro extends beyond its construction. The project faced unique challenges, including TBMs moving through soft clay strata, mining below the bustling Howrah Railway Yard, and navigating a sharp curve in new geological conditions. Obtaining CRS approvals added complexity but offered valuable insights into project management.

Key innovations, such as a highly-skilled tunnel crew, safety measures akin to submarine protocols, and the 'soft eye' design, contributed to the project's success. Special efforts were made to ensure no loss of life or property during TBM operations, with extensive repairs carried out in critical buildings. Traffic diversions, restricted pedestrian movements, and timely evacuations were implemented, emphasizing safety and minimal disruption.

A Triumph of Innovation and Perseverance

India's first underwater metro is not just a feat of engineering but a testament to human resilience and determination. This revolutionary project will redefine commuting between Kolkata and Howrah, offering a swift and efficient alternative to the existing transportation modes. As the underwater metro embarks on its journey, it leaves a trail of inspiration for future infrastructure endeavors, showcasing that even the depths of challenges can't impede progress.


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