Chennai Metro's TBM Kaveri breakthrough at Adyar junction station

CHENNAI: After boring under Adyar river, the bridge across it, petrol stations, hospital, college and several such structures, Kaveri, a tunnel boring machine that had begun work from Greenways station to Adyar junction in February 2023 as part of Chennai Metro Rail phase-2, achieved breakthrough at Adyar shaft on Friday.

According to CMRL, two earth pressure balancing (EPB) boring machines, named 'Kaveri' and 'Adyar', are engaged in tunnelling work. The length of each tunnel from Greenways station to Adyar junction station is 1,228 m. The tunnels pass below Adyar river for a length of 300 m with an overburden of 10-13 m, it added.

The work was challenging, as Kaveri tunnel boring machine (TBM) had to pass through mixed geological conditions like rock at the bottom of the tunnel and sand at the top. “TBM also tunnelled through full-faced hard rock below some portions of the Adyar river. It underwent 65 cutter head interventions (CHI) to replace cutting tools in the TBM face,” CMRL said, adding that changing these tools consumed 178 days.

While tunnelling through, the machine passed below a few petrol bunks, college, hospital, Durgabai Deshmukh Road and Adyar bridge ramp, it noted.

The second TBM, 'Adyar', is currently 277 m away from the Adyar shaft and expected to record breakthrough to the other side by November, CMRL added in a press release.

The Greenways Road station and Adyar junction station are part of the 45.4-km corridor 3 from Madhavaram to Siruseri Sipcot in CMRL phase-2, which runs a total distance of 116.1 km.