The first Tunnel Boring Machine (TBM) installed in Nehru Park in late July to build the underground metro rail station has not been functioning for a few days now.

The cutter, which is one of the principal parts of the TBM, has become worn out and needs to be replaced, Chennai Metro Rail Limited (CMRL) officials said. The cutter has frayed owing to wear and tear.

“It is not necessary that the cutter be changed periodically; it largely depends on the tool’s usage. If it has to drill through hard rock then it wears out soon but in case of loose soil, it works longer,” said an official. A new cutter is expected to be in place in a couple of days, he added.

The first TBM has excavated 90 of the 932 metres it has to cover from Nehru Park to Egmore. The process will be completed by the end of January, CMRL sources said.

Meanwhile, the second TBM at the Nehru Park site will also be commissioned in a few days. Officials plan on starting work for both TBMs on the same day.

Also, 12 temporary rings have been placed inside the tunnel of the first TBM at the Washermenpet site. The TBM there was launched on October 1 and has to tunnel 1349.9 metres to reach Chennai Central Station.

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