The tunnel boring machine (TBM) DIVYA has completed a breakthrough at Victoria metro station, marking the end of the drive between Khidderpore and Victoria on the Joka-Esplanade Metro Corridor. The drive covered one point seven two kilometre (km) beneath central Kolkata and advances the construction of the Purple Line. The milestone follows successive tunnelling stages that linked key stretches of the route and prepares the alignment for station fit-outs and system installations.

The tunnel boring machine measured 95 metre (m) in length and weighed around 600 tonne (t) when assembled. Its outer diameter was six point six metre (m) with a finished tunnel diameter of five point eight metre (m). Precast segments specified at grade M50 and thickness 275 millimetre (mm) were used to line the bore, and two TBMs are being deployed to create twin tube tunnels along the corridor.

Key construction works included a launching shaft excavated inside St Thomas School at Khidderpore measuring 37 metre by 22 metre and 17 metre deep, which served as the lowering and assembly site for the machine. The TBM was manufactured in Chennai and mobilised to Kolkata in March 2025 for assembling and lowering, after which it proceeded beneath urban infrastructure. The tunnelling method transitions to conventional cut and cover beyond Park Street where surface conditions allow.

Earth pressure balancing technology was employed to contend with a high ground water table and soft soil strata typical of the city, with safety systems such as an inflatable seal, pressure transducers and dedicated TSG lines plus a backup TSG pump incorporated into the design. Project authorities described the breakthrough as a significant milestone that accelerates work on station completion and systems integration ahead of planned commissioning phases. The progress is expected to enhance connectivity along the Purple Line and support urban transit capacity once services commence.