First elevated corridor brings newer construction technology


Every new facility for Madurai brings with it new technology coupled with workmanship. When the first Vaigai drinking water project was commissioned, Tamil Nadu Water Supply and Drainage Board engineers brought water through an all-gravity system that required no pumping, all the way from Vaigai dam to the city, in the early 1990s.

Later, when Madurai airport got a new terminal building, the Airports Authority of India introduced the all-steel and glass structure in the late 2000s.

Now, it is the turn of the National Highways Authority of India to give something new. An elevated corridor for 7.3 km on New Natham Road is the first such facility for the city, though Madurai Corporation had planned such a facility at least a decade back.

The NHAI, after putting up foundations, erecting piers and constructing pier caps between Indian Oil Corporation Junction at Tallakulam and Chettikulam beyond Oomachikulam, is now involved in launching girders using next generation girder launchers, which were used in construction of metro rail in Bengaluru and Chennai and other parts of the country.

“The work on elevated highway, a part of Madurai-Natham four-way highway, is progressing ahead of schedule. We started the girder launching work last week and concrete segmental girders meant for one span have been placed,” said NHAI Project Director V. Saravanan.

The project is also introducing newer technology in construction that was hitherto unknown to the Temple City. The work is all about providing a four-way elevated corridor with a width of 17.82 metres with a median running all through. “Constructing the bridge in the conventional method will take at least six years. It will be a very difficult execution on a busy road where traffic cannot be closed for a longer period,” he said.

With this technology, the work is scheduled to be completed in 24 months, whereas even construction of a flyover takes at least 18 months.

The NHAI is using segmental girders that are pre-cast at a yard away from the city and moved one by one to the construction site.

Casting of 35-metre-long girders near the construction site on a busy road is not possible. Similarly, moving such a huge structure, weighing over 800 tonnes, from far off casting yard to the construction site is also impossible. Hence, instead of using a longer girder, smaller segments are cast and later arranged continuously to align them as long girders.

Each segment is being cast to tailor-made measurements to suit the alignment of the highway that has slight curves and sharp bends. “Every segment is numbered and its place of order in the girder is fixed at the drawing table,” said the launching expert M.C.S. Kurup of JMC Projects India that is executing the work.

The girder for each span, which varies between 35 metres and 40 metres, will have 13 or 14 segments each. Each segment weighs around 60 to 70 tonnes. These segments are transported from the yard to the construction site in multi-axle trucks in the night when traffic grows thinner. The role of the launcher comes here to lift the segments up over seven metres and place them in between piers one after the other.

“The heavy machinery physically holds the segments tight till bundles of high tensile steel cables are used for span stressing and span lowering,” he added. As the cables are tightened these segments are transformed into a single mass (girder) and hold them over the piers.

The first launcher is working near IOC Junction, while the second one is under erection near Oomachikulam and the third will be erected near Tiruppalai.

The orange-colour sliding launcher has become an attraction for many curious vehicle users on Gokhale Road who stop for a moment to see what it is doing. Many engineering students from nearby colleges are on internship to learn the new technology for constructing the fish-belly-shaped bridge.

In the conventional method, works like laying foundation, erecting piers and constructing slabs for girders will happen one after the other in a particular order. However, this technology has helped in carrying out various works simultaneously at different locations and thus saves time.

Even as the foundation was being laid and piers constructed, the segmental girders were cast at the yard. Out of the 189 foundations to be laid, 107 have been completed. Similarly, 85 piers (out of 189) have been erected and caps provided for 31 piers in the last eight months, said project manager (JMC Projects) J. Nandakumar. When erection of piers and allied works of constructing utility ducts are going on day and night, the NHAI has been casting the segments at the yard near Oomachikulam.

Besides the work of elevated corridor, widening of the road beyond this structure up to Natham is also going as per schedule.

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Printable version | Feb 20, 2020 9:56:18 AM |

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