Chennai Metro Rail to complete tunnelling work from Royapettah to Thousand Lights next month

After nearly a year and a half, work on the construction of Chennai Metro Rail’s underground network from Royapettah to Thousand Lights for the 118.9-km phase II network will be completed by the end of next month.In corridor 3 of the phase II network covering 45.8 km, trains will depart from Madhavaram and will pass several areas, including Royapettah and Thousand Lights before making the last stop at SIPCOT. Since the underground networks are constructed in small parts, work to build the tunnel from Royapettah to Thousand Lights began early last year.According to officials of Chennai Metro Rail Limited (CMRL), this was one of the toughest stretches for the tunnel boring machine (TBM) to drill through in the phase II project as the near 900-metre stretch hard rock for a substantial length. The machine which started boring from Royapettah has already reached Thousand Lights, but it stands closer to the station, unable to make a breakthrough since the station shaft (receiving point for a TBM in a station) is not ready yet.“The TBMs had to go through the process of cutter head intervention—wherein parts of the cutterhead of the TBM which does the job of boring through the soil— had to be changed as many as 78 times. This is because parts of the cutterhead endure a lot of wear and tear when it bores through rock. At Royapettah, the machine encountered rock at 22 metres below the ground and as the intensity got higher it moved closer to Thousand Lights where the rock was found 16 metres below the ground,” an official said.Construction of the diaphragm wall turned out to be a consuming process at Thousand Lights, he added. “Because of the presence of hard rock, we had to carry out controlled blasting to excavate the site,” he said. Published - September 07, 2026 11:21 pm IST