Chennai Metro Phase II has achieved three Tunnel Boring Machine (TBM) breakthroughs in three consecutive days, marking fresh development in underground construction across Corridors 3 and 5. The breakthroughs were recorded at Kilpauk Medical College (KMC), Villvakkam and RK Salai stations between September 29 and October 1.
Sharing the development on its official X handle, Chennai Metro Rail Limited (CMRL) said, ‘Chennai Metro Phase -II achieves hat-trick of TBM Breakthroughs in three days.”
In another post underlining the accomplishment, CMRL stated, “Kaveri, Marutham and Adyar have officially arrived at their respective stations to keep tunnelling on track.”
For commuters, the three breakthroughs indicate continued growth in the underground construction works being carried out under Chennai Metro Phase II.
Three TBMs reach stations in three days
The series of breakthroughs started on September 29, when Corridor 3 Downline TBM Kaveri reached KMC Station. On September 30, Corridor 5 Downline TBM Maruthan gained its breakthrough at Villivakkam Station. A day later, on October 1, Corridor TBM Adyar reached RK Salai Station.
CMRL termed the three consecutive breakthroughs as a “significant achievement in the ongoing tunnelling works under Phase II.”
Adyar completes 915-metre tunnel
The latest breakthrough came on the underground stretch between Royapettah and RK Salai stations.
Tunnelling between the two stations commenced in September 2024 with the deployment of TBMs Bhavani and Adyar. Upline TBM Bhavani recorded its breakthrough on October 13, 2025, whereas Downline TBM Adyar completed its drive on October 1, 2026.
The Downline tunnel built by Adyar spans 915 metres. The drive commenced on December 29, 2025 and was completed in 277 days.
Tunnel passes critical structures
During the tunnelling drive, Adyar had to pass several critical structures along Royapettah High Road, including Peters Bridge, Andhra School, the EPFO building and several shop lots.
The tunnel was constructed through silty sand with an overburden ranging from approximately 9 to 13 metres. CMRL stated 11 cutterhead interventions were conducted during the drive.
Emphasising the execution of the work in challenging urban conditions, CRML stated the entire drive was completed “without any major ground settlement or adverse impact on existing infrastructure.”
12-km underground section under construction
The work forms part of the 12-km underground section of Corridor 3 between Kellys and Taramani. Larsen & Toubro Limited is responsible for carrying out the tunnelling works, with eight TBMs mobilised for the section.
The Adyar breakthrough also records the 10th TBM breakthrough under the TU02 contract, as per CMRL. Thus, further adds another milestone to the ongoing Chennai Metro Phase II tunnelling works.