Chennai Metro Phase-2 Advances as L&T’s ‘TBM Kaveri’ Breaks Through at Kilpauk 

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CHENNAI (Metro Rail News): Chennai Metro Phase-2 underground tunneling works reached a significant milestone following the successful breakthrough of the Downline Tunnel Boring Machine (TBM) ‘Kaveri’ at the Kilpauk Medical College Station. 

The 685-meters drive by Larsen & Toubro Ltd. passed below active railway tracks, a lake, medical college buildings and existing Metro tunnels, making it one of the more technically sensitive drives on the section. The breakthrough was achieved on the downline between Chetpet and KMC stations after 252 days of tunnelling.

Chennai Metro Phase-2 tackles key tunnelling challenges 

In February 2024, tunnelling commenced between Chetpet Station and KMC station, deploying two TBMs, “Tamarabhaani” and “Kaveri”. On 26 November 2026, the Upline TBM Tamarabharani achieved its breakthrough and on 29 September 2026, the Downline TBM Kaveri completed its drive.

The total length of the tunnel is 685 meters, executed by Larsen & Toubro Ltd. The TBM successfully negotiated several critical structures during the 685 meters drive. Kaveri had to pass:

• Beneath five active Southern Railway tracks near Chetpet Station, with around 18 metres of ground cover.

• Below the Chetpet Eco Park lake.

• Near several Kilpauk Medical College buildings, with ground cover ranging from 21 to 26 metres.

• Close to the existing Phase-I Metro tunnels, with only 6.1 metres of minimum clearance between Phase-I and Phase-II tunnels.

The tunnelling team also carried out 10 cutterhead interventions during the drive. Despite the number of sensitive structures along the alignment, Chennai Metro Rail Ltd. (CMRL) said the drive was completed without any major ground settlement or reported adverse impact on existing infrastructure.

252-days tunnel drive

The downline drive took 252 days to complete. The result is particularly significant at the points where the new tunnel passes below active railway infrastructure and near the existing Metro tunnels. Maintaining ground stability at these locations is critical because even small changes in ground conditions can affect structures above the tunnel.

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