New Delhi: A giant yacht docked in Mumbai harbour, carrying an extraordinary cargo: a pale pink bridge deck that was built in four different countries, weighed the equivalent of about 300 elephants, and required several giant cranes to lift it .
On Wednesday afternoon, 2,300 metric tonnes of deck was lowered between Pier 184 and 185 of the under-construction Sewri-Nhava Sheva Mumbai Trans-Harbour Link (MTHL). It was a milestone not only for the showpiece project or Mumbai itself, but also for India’s engineering and construction prowess in general.
The 22 km long MTHL, considered India’s longest sea link, Peninsular will connect Sewri in South Mumbai Nhava Sheva in mainland Navi Mumbai. It promises that by offering rapid transit between the two parts of the city to unlock the mainland’s commercial and residential potential, and will be an important connector to the under-construction Navi Mumbai International Airport.
The Rs 17,843 crore link is nearing completion, span by span, towards its December 2023 deadline. And in the process, it is marking a first in India’s construction sector, say engineers and officials involved in the project.
One of the first of these, at least for India, is the use of Orthotropic Steel Deck (OSD). These special steel decks enable the span, or distance, between two piers to be three times greater than the norm, and are being used in navigational channel sections for large ships.
Engineers working on the project said the humble pink slab that reached its final destination this week was 180 metres, the longest OSD yet used, which makes its precise launch even more important.
Mumbai Metropolitan Region Development Authority (MMRDA) commissioner SVR Srinivas said, “About 85 to 90 per cent civil work (structural work) has been completed and we are on track to meet the December 2023 deadline.” the in-charge of the project told ThePrint.
“Many of the engineering techniques used in this project have been deployed in India for the first time, and we had to be very careful with everything. Even a small error could be huge and the project could be shelved. can push back.”
MTHL was first fancy Mumbai port about two decades ago as a link that could spur development on the mainland by improving its connectivity with the island city – like Kowloon across Victoria Harbor in Hong Kong.
Between 2005 and 2011, there were three attempts to bid for the project, but all failed for one reason or the other.
In 2016, the Maharashtra government received funding for the project from the Japan International Cooperation Agency (JICA) and awarded with New contract for Link in 2017. Construction eventually began in 2018.
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one period at a time
The OSDs are fabricated in 12 by 12 meter panels in Japan, South Korea, Vietnam and Myanmar before being brought for assembly at the Karanja Port in Uran in Navi Mumbai.
The long spans that these decks give are important for large ships to be able to pass through navigation channels without difficulty.
While a regular span on MTHL is 60 metres, with the use of OSDs, MMRDA has planned spans ranging from 80 to 180 metres.
Every few days, a barge carrying the OSD departs from Carranza Port, pulled by a tug boat.
“We can only move the barge in high water, so we have to be very careful about the timing of the tide. Whenever possible we take advantage of the tide and move very slowly,” advises the project A marine logistics expert from the delivery told ThePrint. Even if the engineers catch a favorable tide, it takes around seven or eight hours for the boat to reach the site location, he said.
The barge measures 100 x 36 meters and weighs 1,300 metric tonnes. Srinivas said that there are three such barges which are carrying the steel deck together.
Wednesday’s launch was the 36th of the 70 OSDs that are being used in the project, which covers about 4 km of the 22 km length of the Harbor Link. Girders are being used for the remaining distance.
“We should be able to launch all the OSDs by August. Even on the remaining 18 km, we have finished launching 90 per cent of the girders,” said Srinivas.
Thereafter, the contractors will install crash barriers along the entire length, sight barriers in part of the sea link with the sensitive Bhabha Atomic Research Area, sound barriers at some places, and then install tolling systems on top of the road with bitumen. MTHL is all set to be operational for public use.
Crash barriers are metal barriers found along roads to reduce the risk of serious accidents. Vision barriers are also frameless structures found on the side of roads to help block the line of sight on either side of the road.
Chief Minister Eknath Shinde, who visited the site of the launch of the OSD on Wednesday, told reporters that the tolling system is likely to be an Open Road Toll (ORT) without any boom barriers to prevent long queues.
first project
Apart from the complex-to-launch OSD, the country’s longest sea link has taken several initiatives.
For years environmentalists disagreed with MTHL’s proposal, fearing that the raucous construction activity would drive away migratory flamingos that appear annually at Sewri Mudflats from December to May.
For this, the MTHL team deployed a method called ‘reverse circulation drilling’ (RCD) for the pile foundation – the first time the technique was used for any project in India – Srinivas told ThePrint.
“Laying of pile foundation is the most time consuming activity in any project. Normally, we resort to vertical drilling with piling machines which create tremendous noise. Four years in a row, such increased noise would have disturbed the habitats of flamingos. The RCD reduces construction noise,” said Srinivas.
“It’s one of the secrets behind flamingo Despite the construction activity coming back year after year,” he said.
MMRDA is also planning to use special high-containment crash barriers from South Korea. An engineer working on the project told ThePrint on condition of anonymity, “Regular crash barriers only take the impact of an accident, but since it is the sea, we want to take every precaution to avoid any untoward incident. were. The high containment crash barriers will push the car back onto the road.”
This is also a new experiment for Indian roads, said the engineer.
(Edited by Uttara Ramaswamy)
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