CHENNAI: Development of dual tunnels for working driverless metro trains awaits the arrival of 23 large tunnel boring machines (TBMs), possible by August.
Officers mentioned tunnelling will start concurrently at numerous places and all 23 TMBs can be operated for sooner development. The 118.9km phase-2 challenge, which has a 2025 deadline, has a 43km underground stretch with 48 stations.
“Tunnelling might begin by September or October, as it could take a while to assemble and deploy the machines underground,” an official mentioned.
Based on officers, 15 TBMs could also be operated to construct corridor-3, which has a 26.7km underground stretch with 30 stations, 4 TBMs every in corridor-4 and 5, which have a ten.1km underground line with 12 stations and a 5.8km underground line with 6 stations respectively.
Officers mentioned they might be tunnelling by means of some difficult places such because the 5km stretch from Nathamuni to Retteri, the place laborious rock soil situation has been recognized. A 1.3km stretch between Nandanam and Panagal Park additionally has rocky soil situations the place TBMs will construct tunnels at a depth of 24m to 26m under the prevailing phase-1 tunnels.
To stop any delay in finishing the tunnelling work, officers mentioned they've determined to assemble tunnels between two consecutive stations, which can be lower than a kilometre, earlier than the TBMs are retrieved and refurbished and launched once more in one other location. This may increasingly not solely pace up the development however any delay in constructing the underground stations is not going to interrupt the tunnelling course of.
“Even when the stations should not prepared, we will begin different works like laying of tracks and cable work within the tunnels as soon as they're accomplished,” the official mentioned.
In phase-1, a TBM at work in Anna Salai was caught close to Authorities Property station for greater than 5 months as a result of the station was not prepared. “We don't need such issues to come up on this section,” an official mentioned.
Delays had been additionally attributable to awarding longer stretches for tunnelling to a single contractor in phase-1 challenge. Nonetheless, officers mentioned utilizing many boring machines on the similar time might value CMRL extra.
Development of 1 kilometre of underground part might value greater than ₹650crore in comparison with elevated part, which can value round ₹250crore.