The Bogibeel Bridge, the longest rail-road bridge in India, stands as a testament to engineering excellence. Spanning 4940 meters over the mighty Brahmaputra River in Assam, this monumental structure connects the city of Dibrugarh with Dhemaji district. The bridge, completed in 2018 at an estimated cost of Rs 5920 crores, serves a dual purpose – a three-lane road on top and a double-line broad gauge railway track at the bottom. This extraordinary infrastructure is not only a symbol of connectivity but also a key element in enhancing the region’s strategic, economic, and social development.
Connectivity Benefits
One of the most significant impacts of the Bogibeel Bridge is its enhancement of regional connectivity. Prior to the bridge, travel across the Brahmaputra was challenging and time-consuming, especially for those traveling between Dibrugarh and other parts of Assam and Arunachal Pradesh. Now, the bridge cuts down the distance between Dibrugarh and Guwahati by 55 kilometers, providing a much quicker route. This reduction in distance is a major convenience for residents, tourists, and businesses alike.
The bridge also links crucial railway lines, such as the Rangia-Murkongselek section on the north bank of the river with the Lumding-Dibrugarh section on the south bank. Moreover, the bridge connects two important national highways: NH-37 (which runs from Assam to Manipur) and NH-52 (connecting Punjab and Karnataka), thereby improving access to the southern states of India.
For the capital city of Guwahati, the bridge has significantly reduced traffic congestion, and its strategic importance goes beyond civilian use. It facilitates the swift transportation of troops and essential supplies to the Tibetan border in Arunachal Pradesh, providing a vital link for national defense.
Construction Overview
The construction of the Bogibeel Bridge is a remarkable feat of engineering, incorporating numerous innovative techniques and technologies. India’s first fully welded warren truss girder-type steel bridge, the Bogibeel Bridge is an exemplar of modern bridge design. The bridge was constructed using an incremental launching technique to erect the superstructure, a process that allowed for the precise placement of steel trusses, making the structure both durable and resilient.
Work on the bridge began in 2002, with the initial surveys and geotechnical tests conducted by Rail India Technical and Engineering Services (RITES), a government-owned consultancy firm. Various contractors took part in this massive project: Bhartia Infra Projects Ltd. (BIPL) constructed the embankments and bunds on the riverbanks, while Gammon India was responsible for laying the foundation of the bridge. The contract to build the steel superstructure was awarded to Hindustan Construction Company (HCC) in 2011.
Technical Construction Details
Substructure Construction: The substructure of the bridge consists of 42 double-D well foundations, each measuring 16.2 m by 10.5 m, with piers made from circular hollow steel tubes. The depth of these foundations ranges between 42 m and 68.75 m, ensuring stability in the face of the river’s shifting waters. Constructing these foundations required massive amounts of materials, including 3 million bags of reinforced cement concrete (RCC) and plain cement concrete (PCC), 2800 metric tonnes of structural steel, and 19,250 metric tonnes of reinforcement steel.
Steel Manufacturing and Fabrication: The Bogibeel Bridge’s steel components were fabricated by India’s largest steel manufacturers, SAIL and Tata Steel. These steel members were meticulously fabricated and welded in a workshop near the southern bank of the river. Using state-of-the-art equipment such as CNC plasma cutting machines and oxy-fuel cutting machines, the steel was shaped to the exact specifications required for the bridge’s design. The fabrication process also involved detailed surface treatment, including gas metal arc welding, to ensure the steel joints were both strong and durable.
Assembly and Launching of Trusses: The steel members were assembled in sequence and then joined using welding techniques. Hydraulic and strand jacks were used to launch the trusses onto the bridge’s foundation. Once a truss was launched, it was welded to the next, and the process was repeated in ten-span segments, each weighing approximately 1700 metric tonnes. This method allowed for precise and efficient assembly of the bridge’s superstructure.
Protective Measures for the Bridge
Given the environmental challenges posed by the region’s climate and seismic activity, several protective measures were incorporated into the bridge’s design to ensure its longevity and safety.
Anti-Corrosive Measures: To combat the high humidity and potential corrosion from the Brahmaputra River, special-grade copper-bearing steel plates were used in the bridge’s construction. The steel components were coated with multiple layers of anti-corrosive materials, including thermal spray aluminum and zinc galvanization, which protect the structure from moisture and other elements that contribute to rusting. This ensures that the bridge remains durable for years to come.
Spherical Bearings: To ensure flexibility and smooth movement of the bridge under varying loads, spherical bearings were used. These bearings, manufactured by Maurer AG in Germany, allow for slight turning and displacement, accommodating the expansion and contraction of the bridge. A total of 164 spherical bearings were used, with four bearings supporting each span of the bridge.
Seismic and Flood Measures: Located in seismic zone-V, the most active seismic zone in India, the Bogibeel Bridge was designed with earthquake-resistant features. Each span of the bridge is equipped with seismic restrainers to prevent unseating during seismic events. Additionally, to address the threat of flooding, dykes were constructed on both banks of the Brahmaputra River. These dykes, reinforced up to 9 km upstream and 7 km downstream, ensure the bridge remains unaffected by the river’s periodic floods.
Conclusion
The Bogibeel Bridge is not just an engineering marvel; it is a critical piece of infrastructure that enhances connectivity, facilitates economic growth, and improves national security. By reducing travel time, boosting trade, and allowing for faster deployment of defense resources, the bridge has transformed the region. With its cutting-edge design and state-of-the-art construction methods, the Bogibeel Bridge sets a new standard for bridge engineering in India and the world. It stands as a shining example of what can be achieved when engineering expertise, technology, and vision come together to address the needs of a growing nation.