India’s infrastructure has undergone significant development, with a constant focus on improving road connectivity. Bridges in India serve as crucial infrastructural components that contribute to the advancement of transportation systems, driving the sector’s growth. This subsector effectively enhances connectivity, particularly in regions that are geographically challenging to access.
Continuing its efforts towards infrastructure development, the centre has inaugurated India’s longest sealink bridge project, the Mumbai Trans Harbour Link (MTHL) on January 12, 2024. Also known as the Atal Setu Nhava Sheva Sea Link, the stretch was developed at a cost of Rs 178 billion. The foundation stone for the project was laid in early 2018, after a significant delay of six decades.
The objective of the project is to improve connectivity in the Mumbai Metropolitan Region, which comprises the districts of Mumbai, Thane, Palghar and Raigad, and promote the region’s economic development.
Project specifications
The Atal Setu bridge is a 22 km long twin-carriageway six-lane bridge over Thane Creek in the Arabian Sea, connecting Sewri in the island city of Mumbai to Chirle in Raigad district on the mainland. It was constructed by the Mumbai Metropolitan Region Development Authority (MMRDA) under the engineering, procurement and construction mode. The sea bridge includes interchanges at Sewri in Mumbai and Shivaji Nagar, Jassi and Chirle on National Highway 4B in Navi Mumbai. It includes a 16.5 km sea link and viaducts on land at both ends with a cumulative length of 5.5 km. The Japan International Cooperation Agency (JICA) funded approximately 80 per cent of the project, with the rest coming from the state and central governments.
According to a study conducted by the MMRDA and JICA, the MTHL will reduce the average travel time between Sewri and Chirle from 61 minutes to less than 16 minutes, while also alleviating congestion on the existing route over the Vashi bridge. During rush hour, one would save around 60-90 minutes. Around 40,000 vehicles are expected to use the bridge every day in 2024. The MTHL allows a maximum speed limit of 100 km per hour. The project was designed to handle a capacity of 75,000 passenger car units per day. As of now, no public transport facilities, such as buses on a dedicated lane, have been announced on the bridge.
Ensuring efficient construction
The balanced cantilever approach was utilised in the construction of the MTHL, an engineering marvel. This strategic approach involves simultaneous construction from both ends, culminating in a meeting at the midpoint. This has not only enhanced efficiency but also enabled the creation of longer and more intricate bridges, representing a paradigm shift from conventional bridge-building methods.
The utilisation of precast concrete segments further underscored the project’s commitment to efficiency. These segments, which are produced in specialised facilities off-site, are later transported to the construction site. By adopting this method, not only was the construction process expedited, but the bridge’s durability, a critical determinant of its enduring structural soundness, was also guaranteed.
The incorporation of orthotropic steel decks is another stand-out feature. These specialised steel decks enable spans that are up to three times longer than standard. This technological innovation has not only enhanced the bridge’s overall efficiency but also created room for a more streamlined and resilient structure, capable of withstanding the test of time. Orthotropic steel deck (OSD) bridges are stronger and have a lower self-weight than composite girder or concrete bridges. Consequently, they require fewer and smaller piers.
The 180 metre long OSD installed on the MTHL bridge represents the world’s longest span length, demanding advanced manufacturing technology and rigorous quality control. OSD facilitates a reduction in construction duration and averts hazards at the site of the undertaking due to its manufacturing process in a factory, requiring less on-site work. Additionally, the use of fewer and smaller piers and a shorter construction period translates to a lesser impact on the environment and ecosystem.
Leveraging technology
The construction of this sea bridge is a testament to the increasing adoption of advanced technologies in India. Some innovative technologies incorporated into the bridge include stone matrix asphalt, reverse circulation drilling (RCD) piling, OSD bridge girders, tuned mass dampers for OSD bridges, an open road tolling system set to facilitate toll collection, full-scale vehicle impact testing for new crash barrier design, and seismic hazard analysis for design.
Boosting the sustainability agenda
The adoption of RCD in the project has not only demonstrated technological innovation but also effectively reduced the environmental consequences associated with large-scale infrastructure projects such as the MTHL project.
The utilisation of trenchless technology for the installation of bridge pier foundations is an innovative method for reducing surface disruptions. This technique allows for the installation of underground utilities without requiring considerable excavation, demonstrating a dedication to environmental sustainability and effective project implementation.
Additionally, Package II of the project utilised recycled concrete slurry and waste to acquire substantial quantities of construction water, aggregates and a rich cement cake. This initiative was led by Tata Projects for the first time.
Safety measures
Given the utmost importance of road safety, anti-crash measures have been implemented. A distinct, divided carriageway with three plus three lanes in each direction has been provided. Concrete, post and rail hybrid anti-crash barriers have been installed on the outer sides of each carriageway.
The MMRDA has allocated one emergency lane on each carriageway to facilitate vehicles in distress in order to prevent bottlenecks on the main carriageway caused by damaged or broken vehicles. Noise barriers have been installed in the mud-flat zone of the primary bridge in order to minimise any potential disruption to flamingos while the bridge is in operation.
Impact on Mumbai’s growth trajectory
Traversing the dense street road network in Mumbai underscores the need for effective and swift transportation alternatives. The MTHL project is a major milestone in the advancement of the city’s transportation infrastructure and has the capacity to transform the way people commute in this busy city.
The project is expected to have a significant influence on the real estate environment in the city and its surrounding areas. This bridge is anticipated to greatly improve connection across multiple mainland areas, including Navi Mumbai, Panvel, Karjat, Kalyan, Badlapur, Dombivli, Turbhe, Ghansoli, Airoli, Ulwe, Dronagiri, Ambernath and Vasai.
Additionally, it would greatly enhance the connectivity between South Mumbai and many key locations such as the under-construction Navi Mumbai International Airport, the Mumbai Pune Expressway, the Mumbai-Goa Expressway and surrounding areas. Additionally, it will enhance accessibility to Jawaharlal Nehru Port. Furthermore, the substantial reduction in travel time will be a game changer for daily commuters in the city.
The project is further anticipated to enhance tourism in the area by facilitating convenient transportation. Consequently, this is anticipated to generate new opportunities for start-ups and businesses operating in the tourism sector.
All in all, the construction of this sea bridge has elevated the transportation infrastructure of the Mumbai metropolitan region. In a country like India, where connectivity via roads fuels economic growth and progress, the MTHL stands out as a link not just between places, but also to a future full of untapped possibilities. With this project serving as a shining example, the bedrock for a more flourishing and interconnected region via road development has now been established.
Harman Mangat