Chennai Metro Rail Limited is preparing to add three tunnel boring machines to Phase II works as underground construction struggles to maintain pace across some of the city’s most difficult sections. The proposed deployment covers stretches around Thiruvanmiyur, Thousand Lights and Thirumayilai, where faster tunnelling could influence both project timelines and future public transport access.
The machines are planned for three demanding sections: Thiruvanmiyur–Taramani, Thousand Lights–Anna Flyover and Mandaiveli–Thirumayilai. Together, these locations sit within Corridor 3, the 45.8-km route linking Madhavaram with SIPCOT. CMRL currently has 23 TBMs working across the Phase II network, according to its published project information. The wider expansion covers 118.9 km and 128 stations, with completion targeted for the end of 2028. Corridor 3 contains the largest underground component, extending about 26.7 km.The additional equipment is being considered against a significant tunnelling gap. Of the 43.04 km of twin-track tunnelling planned for Corridor 3, 19.68 km has reportedly been completed, leaving 23.36 km still to be excavated. The proposed procurement is estimated at around ₹180 crore.
The challenge, however, is not simply a shortage of machinery. Construction has also been affected by delays in underground station works, shaft readiness and utility relocation. These dependencies matter because TBMs cannot operate continuously without suitable launching, retrieval and station interfaces.That distinction is important for Chennai. Adding machines can increase excavation capacity, but it cannot by itself resolve bottlenecks elsewhere in the construction chain. CMRL’s own technical documentation shows that Phase II involves complex underground engineering, including tunnels beneath existing Metro infrastructure and deep stations in narrow urban corridors. Recent progress suggests that the tunnelling programme is nevertheless moving forward. CMRL recorded its 24th Phase II tunnel breakthrough in early August, indicating that several delayed drives are now advancing.
For residents and businesses along the southern and central corridors, the larger issue is when construction translates into usable connectivity. Faster tunnelling could reduce the duration of surface disruption and bring high-capacity public transport closer to employment districts, residential neighbourhoods and major interchange points. The next test will be coordination. CMRL will need station shafts, utility shifts, civil works and tunnelling to progress together. Without that synchronisation, more TBMs may increase capacity without delivering the schedule certainty that Chennai’s rapidly expanding urban economy increasingly needs.
