CHENNAI: The construction work of the 3.2-km Teynampet-Saidapet four-lane elevated corridor above the Teynampet and Nandanam Metro stations is set to resume soon, with CMRL recently granting permission to the state highways to carry out the work.
Official sources said deck slab work had been completed along 2.3 km, while the construction above the two metro stations had remained stalled on Anna Salai for the past few months.
After minor variations were noticed in the original design submitted by the state highways, CMRL appointed a Japanese consultant to review the design and suggest necessary modifications for erecting portal frames above the two metro stations.
Following a joint study by the state highways and the consultant, it was found there were no major flaws in the design. The consultant recommended installing portal frames along a 300 m stretch at 15m intervals above the two metro stations.
Accordingly, CMRL recently granted permission to the highways to proceed with the construction work. A portal frame is a rigid structural frame that connects two columns via a beam.
“While steel piers are being erected for laying concrete deck slabs along the entire corridor, portal frames will be used for the 300m stretch above the two metro stations. The decks will be placed on the portal frames.
The two legs of the portal frames will be positioned directly on the walls of the metro stations, which are located 14-15m below the road. The corridor is expected to be ready by March next year and no further approval is required from any agency, except for traffic diversions,” a senior highways official said.
Of the total 3.2km stretch, 2.4km passes directly above the metro tunnel, including a 460m stretch over the Teynampet and Nandanam metro stations. The remaining 655 metres runs along the non-metro stretch, excluding the entry and exit ramps.
Another official said around 2.3 km of the flyover had been completed and 50 of the total 69 piers has been erected. “The remaining works will be expedited. Erecting the portal frames alone will take a minimum of three to four months,” the official added.
The labour shortage that had affected the manufacturing of prefabricated steel components in other states has now been resolved and the work is progressing in full swing. “However, construction work is permitted for only six hours a day, due to which the pace of work remains slow,” the official added.
The 3.2km project, touted as the country’s first elevated corridor to be built directly above an operational metro tunnel, is being constructed using prefabricated steel components. As the flyover runs above the underground metro line, the engineering complexity has pushed up the project cost to `621 crore, making it costlier than a conventional highway project.
The Teynampet-Saidapet metro tunnel runs at a depth of 14-15m beneath Anna Salai. To avoid disturbing the tunnel, the highways department drilled only up to a depth of 7m from the road surface to lay the flyover’s foundations.
Quick look
CMRL approves construction of flyover above Teynampet and Nandanam metro stations
About 2.4 km of the 3.2 km corridor runs directly above the metro tunnel
Of the 460 m stretch above the two metro stations, permission was granted to erect portal frames along 300 m
Two-legged portal frames to be installed above the metro stations
Project deadline extended to March 2027