Chennai Metro Update: TBM Kolli Completes Challenging 903-Meter Tunnel From Ayanavaram To Otteri

The tunnel boring machine (TBM) named Kolli (S 81) began its work on July 11, 2023, digging a tunnel from Ayanavaram Station to Otteri Station, covering a distance of 903 meters. The tunneling was completed on August 29, 2024, when the machine broke through at the Otteri shaft. This marks the 6th successful breakthrough by Tata Projects Limited under the TU-01 contract. In total, CMRL has achieved 7 TBM breakthroughs in the Phase-2 project, the Chennai Metro Rail Limited (CMRL) said in a statement on Friday.

The tunnel section between Ayanavaram and Otteri was one of the most challenging parts of the project. The first 500 meters of the tunnel had to navigate a sharp 220-meter radius curve, and the last 200 meters had to deal with a 280-meter radius curve. The tunneling also had to pass through densely populated areas and manage over 100 bore wells, ensuring alternative water sources for the public without any disruptions.

The entire tunneling process was carefully managed, with strict monitoring to ensure that the ground above the tunnel remained stable and that there were no problems for the surrounding areas.

The CMRL has begun expanding the city's metro network as part of Phase II, following the successful completion of Phase I and its extension. This expansion includes three new metro corridors, adding a total of 116.1 km to the network.

Corridor 3 runs from Madhavaram Milk Colony to Siruseri Sipcot, covering 45.4 km from north to south across Chennai. It will include 28 underground stations and 19 elevated stations.

Corridor 4 spans 26.1 km from the Light House station near the beach to the Poonamallee Depot, running east to west. This corridor will feature 9 underground stations and 18 elevated stations.

Corridor 5 also starts at Madhavaram Milk Colony and runs 44.6 km, passing through key areas like Koyambedu, Porur, and Alandur before reaching Sholinganallur. It will have 6 underground stations and 39 elevated stations.

For Corridor 3, the first 9 km of underground construction, from Madhavaram Milk Colony to Kellys, is being handled by Tata Projects Limited, using 7 tunnel boring machines (TBMs) to carry out the work.