Chennai Metro Rail (CMRL) has recorded the ninth tunnel boring machine (TBM) breakthrough under Phase-II after TBM Kaveri reached Kilpauk Medical College Station. The machine completed a 685-metre underground drive from Chetpet as part of the downline tunnelling works for Corridor 3.

Larsen & Toubro executed the downline drive, which was completed in 252 days. During the operation, the TBM negotiated several technically challenging sections, including five live Southern Railway tracks, the Chetpet Eco Park lake and buildings located within the Kilpauk Medical College campus.

The machine passed beneath the railway tracks with an approximate overburden of 18 metres. The sections below the lake and college buildings had overburden ranging from 21 to 26 metres, requiring the tunnelling operation to maintain controlled progress through varying underground conditions.

The work was also carried out near existing Phase-I Metro tunnels. A minimum clearance of 6.1 metres was maintained between the Phase-I and Phase-II tunnel networks during the drive. CMRL said the operation was completed without any major ground settlement or adverse impact on existing infrastructure.

The tunnelling operation involved ten cutterhead interventions. The Chetpet-Kilpauk Medical College section used two TBMs, with Tamarabharani assigned to the upline and Kaveri working on the downline. Tamarabharani achieved its breakthrough on 26 November 2025, completing the corresponding tunnel drive for the section.

Kaveri’s latest breakthrough marks the ninth TBM breakthrough under the TU02 contract for Corridor 3 of Chennai Metro Phase-II. The milestone advances tunnelling works on a section that passes beneath active railway infrastructure, a lake and institutional buildings before reaching the Kilpauk Medical College Station area.