Kolkata Metro Purple Line: TBMs Durga and Divya complete Kidderpore–Victoria tunnels
Synopsis
Both tunnels of Kolkata Metro's Purple Line between Kidderpore and Victoria are now fully bored — TBM 'Divya' broke through on 11 August, weeks after 'Durga' did on 10 July. It is a quiet but consequential milestone in a project that has battled soft soil, military land permissions, and depot disputes to inch Joka closer to Esplanade.
Key Takeaways
TBM 'Divya' achieved a breakthrough at Victoria station on 11 August 2026 , completing the second tunnel between Kidderpore and Victoria .
TBM 'Durga' had completed the first tunnel at the same station on 10 July 2026 ; tunnelling in this section began on 11 October 2025 .
The completed tunnel stretch is 1.72 km long with a finished diameter of 5.80 metres .
Each TBM is 95 metres long, weighs nearly 600 tonnes , and uses Earth Pressure Balancing technology suited to Kolkata's soft soil.
Metro services are already running between Joka and Majerhat ; the full corridor will eventually link Joka's IIM campus to Esplanade .
The project has faced delays from land acquisition, Local Military Authority permissions, and Maidan club relocations.
Metro Railway, Kolkata, has completed boring of both tunnels between Kidderpore and Victoria stations on the Joka–Esplanade Metro Corridor (Purple Line) after Tunnel Boring Machine 'Divya' achieved a breakthrough at Victoria station on Tuesday, 11 August 2026. The milestone, reached around noon, marks a significant leap forward in one of the city's most complex urban infrastructure projects.
Key Developments
The breakthrough was witnessed by Prem Sagar Gupta, General Manager, Metro Railway, Kolkata, along with senior officials of Rail Vikas Nigam Limited (RVNL) — the executing agency — and L&T. TBM 'Durga' had already completed its run at the same station on 10 July 2026, having started tunnelling from Kidderpore on 11 October 2025. With 'Divya' now through, the 1.72 km twin-tube tunnel stretch between the two stations is fully bored.
Engineering Challenges and How They Were Addressed
Kolkata's notoriously high groundwater table and soft alluvial soil demanded specialised machinery. Earth Pressure Balancing (EPB) type TBMs were deployed to manage these conditions. Each machine is 95 metres long, weighs approximately 600 tonnes, and is fitted with inflatable seals, pressure transducers, TSG lines, and Backup TSG Pumps. The finished tunnel diameter stands at 5.80 metres, achieved using precast concrete segments of M50 Grade, each 275 mm thick.
A launching shaft measuring 37 metres in length, 22 metres in width, and 17 metres in depth was constructed inside St Thomas School on Diamond Harbour Road in Kidderpore. The 6.60-metre diameter TBM was manufactured in Chennai and mobilised to Kolkata in March 2025 for assembly and lowering. Officials noted that tunnelling was carried out without disrupting surface traffic or daily life in this densely populated part of the city.
What Comes Next on the Purple Line
Beyond Park Street, tunnelling will shift to the conventional Cut and Cover method. The stretch from Joka to Kidderpore will be elevated. Metro services are already operational between Joka and Majerhat. Once the full corridor is complete, it will link Joka — home to the country's first Indian Institute of Management (IIM) — directly to the city's central business district at Esplanade.
Hurdles the Project Has Faced
The Joka–Esplanade corridor has not been without setbacks. Land acquisition issues at the Joka depot, delayed permissions from the Local Military Authority (LMA) for land on the Kolkata Maidan, and the temporary relocation of several Maidan clubs have all slowed progress at various stages. The completion of the Kidderpore–Victoria bore is being seen as a turning point that demonstrates the project can overcome its structural obstacles.
With both tunnels now bored in this critical section, attention shifts to civil finishing, station fitouts, and the remaining tunnelling segments that will eventually bring the Purple Line to Esplanade.
Frequently Asked Questions
What is the Joka–Esplanade Metro Corridor (Purple Line)?
The Joka–Esplanade Metro Corridor, known as the Purple Line, is an under-construction metro route in Kolkata that will connect Joka in the south to Esplanade in the city centre. It will pass through Kidderpore, Victoria, and Park Street, among other stations, and is being executed by Rail Vikas Nigam Limited (RVNL).
What did TBM 'Divya' achieve on 11 August 2026?
TBM 'Divya' broke through at Victoria station on 11 August 2026, completing the second of two tunnels between Kidderpore and Victoria stations. This followed TBM 'Durga's' breakthrough at the same station on 10 July 2026, meaning the full 1.72 km twin-tube tunnel stretch is now bored.
What technology is being used for tunnelling in Kolkata?
Earth Pressure Balancing (EPB) type TBMs are being used to handle Kolkata's high groundwater table and soft soil. Each TBM is 95 metres long and weighs nearly 600 tonnes, equipped with inflatable seals and pressure transducers to manage ground conditions safely.
Where are Metro services currently running on the Purple Line?
Metro services are already operational between Joka and Majerhat. The remaining sections, including the underground stretch through Kidderpore, Victoria, and onward to Esplanade, are under construction.
What challenges has the Purple Line project faced?
The project has encountered land acquisition difficulties at the Joka depot, delayed permissions from the Local Military Authority for land on the Kolkata Maidan, and the temporary relocation of several clubs on the Maidan. These hurdles have contributed to delays in the corridor's overall completion timeline.
