Chennai Metro Phase II: TBM Adyar Completes Tunnel Breakthrough at RK Salai Station

Chennai Metro Rail Limited (CMRL) has achieved another major milestone in its Phase II project, with the downline tunnel boring machine (TBM) named Adyar completing its breakthrough at RK Salai Metro station on Corridor 3. The achievement marks the third consecutive TBM breakthrough in three days, highlighting the progress of underground metro construction in Chennai.

TBM Adyar Completes 277-Day Tunnelling Operation

The TBM Adyar began tunnelling from Royapettah Metro station on December 29, 2025, and completed its drive at RK Salai station after 277 days of work.

During the operation, the machine navigated several challenging sections along Royapettah High Road, passing beneath or near critical urban structures, including Peters Bridge, the Employees` Provident Fund Organisation (EPFO) building, Andhra School and multiple commercial shop lots.

The tunnel was constructed through silty sand, with an overburden of approximately 9 to 13 metres. A total of 11 cutterhead interventions were carried out during the tunnelling process.

According to CMRL, the operation was completed without major ground settlement or adverse impacts on existing infrastructure despite the complex urban environment.

Chennai Metro Achieves Three TBM Breakthroughs in Three Days

The latest milestone follows two other TBM breakthroughs achieved under Chennai Metro Phase II.

September 29, 2026: Corridor 3 downline TBM Kaveri completed its breakthrough at Government Kilpauk Medical College (KMC) Hospital Metro station.

September 30, 2026: Corridor 5 downline TBM Maruthan achieved its breakthrough at Villivakkam Bus Terminus Metro station.

October 1, 2026: Corridor 3 downline TBM Adyar completed its tunnelling drive at RK Salai Metro station.

These consecutive achievements mark a significant tunnelling milestone for Chennai Metro`s ongoing underground construction works.

Corridor 3 Underground Metro Construction

The 12-km underground section of Corridor 3 between Kellys and Taramani is being constructed by Larsen & Toubro, with eight tunnel boring machines deployed for the work.

The Royapettah–RK Salai tunnelling section also involved an earlier drive by the upline TBM Bhavani, which began tunnelling in September 2024 and completed its breakthrough in October 2025. The downline TBM Adyar has now completed the corresponding drive.

Chennai Metro Phase II Progress

The successful completion of the Adyar tunnelling operation represents another step forward for Chennai Metro Phase II. Underground tunnelling in densely developed parts of the city requires careful coordination, ground monitoring and measures to protect existing buildings and infrastructure.

With three TBM breakthrououghs achieved over three consecutive days, CMRL has recorded a series of important construction milestones as work continues on the Phase II network.