Project Profile: Kolkata East-West Metro (Green Line 2)

The Kolkata Metro Line 2, or the East-West Corridor, represents a landmark achievement in Indian urban rail infrastructure, distinguished by the nation’s first underwater metro tunnel beneath the Hooghly River. This project profile details the advanced engineering, international collaboration, and technical specifications that overcame significant geological and logistical challenges. It serves as a critical case study in modern tunneling and large-scale infrastructure project management.

Technical Specifications

The core of this project is its 10.8 km of twin underground tunnels, which include a 520-metre section constructed 33 metres below the riverbed of the Hooghly River. The tunnels feature an external diameter of 6.1 metres and an internal diameter of 5.55 metres. Construction in the challenging sub-alluvial geology necessitated the use of two advanced Earth Pressure Balancing (EPB) Tunnel Boring Machines (TBMs), named Prerna and Rachna, supplied by the German manufacturer Herrenknecht AG. These machines enabled rapid excavation while minimizing ground subsidence in the dense urban environment.

The tunnel lining is comprised of M50-grade, pre-cast reinforced concrete segments, each 275mm thick. Six of these segments form a complete ring, engineered for extreme durability. To ensure water tightness, particularly in the subaqueous section, the concrete mix was enhanced with fly ash and micro-silica to reduce permeability. This structural integrity is further secured by a dual-seal system, featuring German-made neoprene and hydrophilic gaskets, and a two-component grout mix that prevents any water ingress, a critical requirement for operating under a major river.

Safety infrastructure meets stringent international standards, complying with National Fire Protection Association (NFPA) 130 guidelines. The project incorporates two emergency evacuation shafts, up to 760 metres long, strategically located at Howrah Station and Strand Road. These are complemented by a high-capacity ventilation system and continuous walkways throughout the tunnel length, ensuring safe egress for passengers during any emergency scenario.

Key Takeaways

• Benchmark in Underwater Tunneling: The project successfully established India’s first underwater metro line, providing a critical engineering blueprint for future subaqueous infrastructure projects in the country.
• Success of International Collaboration: The seamless partnership between Indian (Afcons), Russian (Transtonnelstroy), German (Herrenknecht), and Japanese (JICA financing) entities highlights the value of global expertise in executing complex megaprojects.
• Advanced Geotechnical Solutions: The deployment of sophisticated EPB TBMs and specialized waterproofing technologies proved highly effective in navigating the soft clay geology of Kolkata, setting a new standard for urban tunneling in challenging soil conditions.

Frequently Asked Questions (FAQ)

What is the main engineering achievement of the Kolkata East-West Metro?

The primary engineering achievement of the Kolkata East-West Metro is the construction of India’s first-ever underwater transportation tunnel. This 520-metre section runs beneath the Hooghly River, connecting the cities of Howrah and Kolkata, and was completed in a record 66 days using advanced tunnel boring technology.

Which companies built the challenging underground section of the East-West Metro?

The underground tunneling work, including the underwater section, was executed by a joint venture between Afcons Infrastructure, an Indian firm, and Transtonnelstroy, a Russian company. The specialized Tunnel Boring Machines (TBMs) were manufactured by Herrenknecht AG of Germany, with the project being implemented by the Kolkata Metro Rail Corporation (KMRCL) and supported by the Japan International Cooperation Agency (JICA).