It is yet another engineering feat that has been accomplished by the Kolkata Metro in the form of the successful breakthrough of TBM ‘Durga’ at the site of the under-construction Victoria Metro Station. This feat is the accomplishment of the twin tunnels of Khidderpore and Victoria of the Purple Line (Joka-Esplanade Corridor). This breakthrough is an example of the swift pace of construction in the underground and is indicative of the engineering prowess required to construct a metro in the busy and historically significant part of Kolkata.
A Historical Milestone for the Purple Line
Purple Line: One of Kolkata Metro’s Most Ambitious Projects, To Connect Joka With Esplanade Via Both Elevated and Underground Segments
Whereas train services are already running on the elevated segment of the Joka-Majerhat line, the underground portion between Khidderpore and Park Street is regarded as the toughest challenge of the entire project. The successful entry of tunnel boring machine ‘Durga’ into Victoria station can be seen as completing the initial phase of tunnelling for the line.
Durga TBM Journey
TBM Durga made her first underground journey starting on 10 July 2025 from an engineered launch shaft within the boundaries of St. Thomas School in Khidderpore. This huge equipment was responsible for cutting 1.7 kilometers of tunnels up to Victoria Station. On this trip, Durga made cuts of the soil while installing reinforced concrete tunnel rings, resulting in an underground path for future metro trains. In about one year of continuous operation, Durga came out successfully at Victoria Station, thus completing her first mission.
Why This Breakthrough Is So Important
While building tunnels, a breakthrough is certainly the most important achievement. A breakthrough means reaching the point where the tunnel boring machine was supposed to reach by traveling an underground distance. It indicates for the engineers that they have excavated successfully and safely despite all the geotechnical and structural difficulties. In light of the fact that the Purple Line runs underneath a number of crowded localities and some historic sites, finishing off this section successfully becomes quite a great engineering feat.
Engineering Success under Historic Kolkata
Excavation of underground tunnels in central Kolkata is not an easy job. It involves passing very close to heritage monuments like the Victoria Memorial, various government buildings, hospitals, and road intersections. Continuous monitoring of ground motion was essential to prevent the effects of excavation on the structures and traffic above ground. With the use of modern EPB TBM (Earth Pressure Balance Tunnel Boring Machine) technology, the engineers were able to excavate while ensuring stability even when they encountered various types of soil during excavation.
The Technology Behind TBM ‘Durga’
TBM Durga is an extremely complex machine that is almost 95 meters long and weighs approximately 600 to 650 tonnes. This particular machine can dig through the ground and line the tunnels with precast concrete sections at the same time, ensuring the longevity and safety of the structure. Tunnel Boring Machines are better than conventional digging systems as they have minimal impact on the surface and hence are suitable for building tunnels under congested urban cities.
What happens next?
However, Durga has finished the Khidderpore–Victoria link and the Purple Line still remains under construction. Another tunnel boring machine called ‘Divya’ is excavating a parallel tunnel using the same path. Having finished with the first stage, both the machines will move towards Park Street to construct yet another crucial section of the underground tunnel. On completion of the tunnelling process, the engineers will start laying down tracks, signals, ventilation, electrification, communication system, and other related infrastructures required for starting passenger services.
Advantages for the People of Kolkata
The completion of the Purple Line will definitely enhance public transport in Kolkata. The metro line will help to link the southern suburbs with the city center, thus cutting down the journey time and reducing traffic from the busy roads. Such places like Joka, Majerhat, Mominpore, Khidderpore, Victoria, Park Street, and Esplanade will be better served through efficient metro systems. This project will definitely increase the use of public transport, reduce fuel consumption, minimize traffic congestion and promote a cleaner urban environment.
Metro expansion will definitely help boost economic growth through the enhanced connectivity with commercial centers, educational institutions, tourist centers, and government offices. Better mobility has always been linked with increased business operations and better property prices, and hence the Purple Line will certainly be an investment worth considering for Kolkata in the future.
A Step Towards Kolkata’s Metro Expansion
One of the largest expansions of the metro line Kolkata, India’s first metro city, is experiencing currently in its history. In addition to the East-West Metro and several other new lines, the Purple Line will definitely change the transportation scenario of the city in the coming years. With each engineering feat accomplished like the breakthrough made by the Tunnel Boring Machine (TBM) Durga, the city gets one step closer to an integrated public transportation system.
Effective coordination between Metro Railway, RVNL, the engineers, the contractors, and technical personnel involved in this project working under tough urban conditions has helped make this achievement possible.
Conclusion
The successful achievement of Tunnel Boring Machine ‘Durga’ at Victoria Station is not only a landmark event in terms of construction but also reflects engineering ingenuity and the continuous effort of Kolkata to become an advanced, interconnected city. The fact that the completion of the first tunnel under ground from Khidderpore to Victoria indicates that the difficult Purple Line construction is making progress regardless of the geophysical difficulties. With the ongoing process towards Park Street and then Esplanade, people residing in Kolkata will enjoy enhanced metro connectivity in terms of speed, safety, and efficiency.
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