Underwater tunnel from Greenways Road to Adyar for Chennai Metro Rail’s phase II project ready

After a gruelling battle to cut through rock, Chennai Metro Rail has finally completed building an underwater tunnel connecting Greenways Road with Adyar in the city. 

After a gruelling battle to cut through rock, Chennai Metro Rail has finally completed building an underwater tunnel connecting Greenways Road with Adyar in the city. 

As part of the ₹63,246-crore phase II project, Chennai Metro Rail commenced the work to build an underwater tunnel from Greenways Road to Adyar in February last year, and the earth pressure balancing tunnel boring machine (TBM) named ‘Kaveri’ was set in motion. The other TBM, ‘Adyar’, is set to reach Adyar station in two months and has another 277 metres left to hit the target.

This short stretch of 1.2 km between Greenways and Adyar falls under corridor 3 of the phase II project, whose starting point is Madhavaram and end point is SIPCOT, and covers 45.4 km.

According to officials of Chennai Metro Rail Limited (CMRL), it took almost a year and half for the TBM Kaveri to bore under the Adyar river and land at Adyar station owing to difficult ground conditions. Though the machine bored under the Adyar river for a length of 300 metres, it was quite a laborious process as it was faced with hard rock. This aside, there were also some parts wherein the machine had to wade through mixed geological conditions like handling hard rock and sand. 

The TBMs tools had to be changed intermittently as a result. There were 65 cutter head interventions (replacement of cutting tools) and this took as many as 178 days. 

The TBM Kaveri has bored under Dr. MGR Janaki College, a few petrol bunks, Andhra Mahila Sabha Hospital, Durgabai Deshmukh Road, and Adyar bridge ramp.

Officials had previously spoken about the difficulties of drilling under mixed geological conditions and how it slowed down the TBMs.