Soon, tunnel boring machines (TBM) will crawl through the city’s underbelly to lay two tracks side by side for Chennai Metro’s phase II work.
According to CMRL officials, as many as 15 TBMs will arrive in the city from different parts of the country and the world to build 21 km of tunnels from Madhavaram to Taramani for the phase II project.
The TBMs will be deployed at multiple locations in this 21-km stretch and will bore two passages for train movement, officials said. These machines can weigh nearly 800-900 tonnes, with a length of 80-90 m. That is, if a TBM stood vertically, it will be like a 25-storey building, officials said.
These machines will drill about 5 m a day, which may also be much lesser if the soil conditions are challenging. In the phase I project, only 12 machines were employed for 24 km. For phase II, more TBMs will be used to finish the job early, the officials said.
After the machines arrive, it will take nearly six months to carry out initial preparatory work to launch the TBMs and then the actual boring work will begin, officials note.
“The geological conditions of the city are difficult to execute the underground boring work. But we have done soil testing in most locations and have planned it in such a way that we stick to the deadline and finish the work as early as possible. We are hoping that the whole tunnelling work will be over for these 21 km in two years,” an official said. Only recently, tenders were called for building the tunnels for the phase II project. In two months, the CMRL will award two contracts — one for constructing a tunnel from Madhavaram to Kellys and another from Kellys till Taramani, officials said. Afterwards, the CMRL will float tenders to execute the building of stations along this stretch.
