Today prime minister Narendra Modi will inaugurate the Bogibeel bridge over the Brahmaputra river in Assam. At 4.94 kilometer, this will be India’s longest Rail cum Road bridge. The first bridge over the Brahmaputra in upper Assam or eastern Assam, it will connect Dhemaji district on the north with Dibrugarh district in the south. The bridge has a three-lane road on the top deck, while the deck below carries two broad gauge railway tracks. This is around 100 km away from India’s longest bridge, the 9.76 km long Dhola-Sadiya bridge over the Lohit river, one of the three rivers that form the Brahmaputra river.
Like most other infrastructure projects in the state, this bridge also took a very long time to be completed. A bridge at this location was a demand of the people for several decades. Finally, in January 1997, the then prime minister H D Deve Gowda laid the foundation stone for the bridge. But that was limited to a foundation stone only, with no progress in the project. After a delay of 5 years, construction of the bridge was officially started by former prime minister Atal Bihari Vajpayee in 2002, with a target to complete the construction by 2009.
State-run Rail India Technical and Engineering Services (RITES) undertook the pre-construction evaluations, geotechnical studies and prepared the detailed design of the bridge. But again, the project fell into more delays, and by 2011, only the major earthwork, building of guide bunds and dykes were completed. The river swells to more than 10 km during the monsoon at the location of the bridge, that distance was narrowed down to around 5 km with the help of guide bunds on both the banks of the river. The actual construction of the bridge started in 2011, with the work on the substructure of the bridge.
Gammon India won the contract for substructure, which included the well foundations and pillars for the bridge. Due to annual floods, most of the work on the substructure could be carried out only for 4-5 months a year, which caused delays in the progress of the construction. The bridge has 42 pillars, with a span length of 125 meters.
The contract for the superstructure of the bridge was won by a consortium of Hindustan Construction Company (HCC), VNR Infrastructures and Germany-based DSD Brouckenbau. The superstructure is made of composite welded steel truss, and it is the first fully welded bridge of Indian Railways. The upper road deck is made of Reinforced Cement Concrete.
The contractors for the superstructure had set up fabrication, assembly and paint units on the south bank of the river, where the entire spans were welded together before launching on to the pillars using a launching unit. Several steel-working technologies were used for the first time in India in the construction of the bridge. Technologies from Sweden and Denmark have been used to build the structures. As the bridge is fully welded, it has resulted in the reduction in weight compared to riveted steel bridges.
The spans were launched onto the substructure using a mechanism of hydraulic jacks and cables. Using this system, the spans were pulled to the northern end of the bridge, while newer sections were added at the southern end. 1000 tonne hydraulic jacks were used to launch the spans, which were moved as a set of 10 spans. With each span weighing 1700 tonnes, the pulling power required to pull 10 spans at a time was equal to the power required to pull 26 Airbus A380 aircraft with maximum take-off load of over 650 tonnes, that too without wheels. The process of construction of the bridge is explained in this animated video:
A total of 78,000 tonnes of steel has been used in the bridge, equivalent to 10 Eiffel towers. Essar Steel supplied 20,000 tonnes of high strength steel plates for the superstructure. State-run Steel Authority of India Limited (SAIL) supplied around 35,400 tonnes of steel, which included TMT bars, plates, and other structural elements. As corrosion protection measures, apart from using special grade copper-bearing steel plates, a complex system of metallizing, hot zinc spray, epoxy, and aliphatic polyurethane coating was applied to the superstructure.
The initial sanction cost for the bridge was ₹3,230 crore, which includes land acquisition, earthwork, railway tracks and approach roads on both sides of the Brahmaputra river including bridges etc, apart from the main bridge. But the cost was increased to ₹4,857 crore as a result of cost escalation due to delays and few design changes, including the increase in the length from 4.31km to 4.94 km.
The bridge will connect the two railway lines and two national highways that run parallel on both sides of the Brahmaputra river. The railway track over the bridge will join the North East Frontier Railway’s Rangia-Murkongselek section on the north bank with the Lumding-Dibrugarh section on the south bank of the Brahmaputra river. On the other hand, the road link will connect National Highway 52 on the north side with the National Highway 37 on the southern side (as per old highway numbering system).
As the areas on the north side of the river are relatively less developed compared to the areas on the south side, people in Lakhimpur, Dhemaji districts will be immensely benefitted from the bridge. Dibrugarh, the second largest city in Assam, is just 15 km away from the bridge. Other than Assam Medical College and Hospital, this city is home to several private hospitals, Dibrugarh University, and many other educational and other important intuitions. Dibrugarh and nearby Tinsukia are also important trade hubs.
The bridge also provides a direct link between Dibrugarh and Itanagar, the capital city of Arunachal Pradesh. It will also provide an important link for people in Arunachal. Apart from providing direct access to places in Assam on the southern bank of Brahmaputra, it will also provide them with a direct link with the part of Arunachal that lies south of Assam, bordering Nagaland and Myanmar.
The Bogibeel bridge will be the third rail-road bridge over the Brahmaputra, and the fifth overall. The first bridge over the Brahmaputra river in Guwahati, the Saraighat bridge, is a rail-road bridge. The other rail‑road bridge is the Naranarayan Setu in the western part of Assam. Rest two are road only bridges, one of them near Tezpur in central Assam, and the other one is parallel to existing Saraighat bridge in Guwahati, which was completed last year after a long delay. Work on a second road bridge parallel to the Kalia Bhomora Setu near Tezpur is already going on.
Several other bridges over the mighty river have been announced in recent times. One of them is the 20-kilometer long Dhubri-Phulbari Bridge at the eastern end of Assam. It will be the longest bridge in India, DPR for which had been already finalised. Three more bridges over the Brahmaputra in Guwahati have been planned. Two of them have been approved and work will start soon, one at the eastern end of the city near Narengi, the other at the heart of Guwahati at Bharalumukh. The third bridge near Palashbari in the east is in the planning stage. Apart from that, four more bridges will be built at various locations in the Assam over the Brahmaputra between Guwahati and Dibrugarh.