Extreme Engineering Chenab Railway Bridge

Soaring 1,177 feet above the Chenab river is the world’s highest single arch railway bridge, standing 359m above the riverbed – 35m higher than the Eiffel Tower. While multiple partners were involved in the design of the bridge including IISc-Bangalore along with key overseas consultants, the lead consortium partner in the JV for construction was India’s Afcons Infrastructure Limited.

Chenab Railway bridge is designed to withstand high wind speeds up to 266 km/hr and bear earthquakes of the highest zone-V intensity. Vital for improving connectivity, promoting regional development, and enhancing India’s strategic infrastructure in J&K, the Chenab River Bridge is constructed in the seismically active and geologically complex Himalayan region and engineers have had to overcome unique challenges such as unstable rock slopes, landslides, and harsh weather conditions.

 

For the first time in Indian Railways, incremental launching was done on transition curve and a longitudinal gradient, both occurring at same location, for the deck launching of the viaduct portion of the Chenab Bridge. Typically, bridges have been constructed incrementally on a straight or a curved platform with a uniform radius. Executing launching activities in inclement weather & stormy wind conditions was extremely challenging.

– Giridhar Rajagopalan,

Deputy Managing Director, Afcons

Constructed over the Chenab river in the Kouri region of the Reasi district, the bridge features 98 deck segments and is a part of the much-anticipated 272-km-long railway line from Udhampur to Baramulla. It is 1315m long and will remain operational at a restricted pace of 30 km/hour even after removing one pier/trestle. The bridge’s construction involved the fabrication of 31,121 MT structural steel, 10 lakh cubic metres of earthwork, 66,000 cubic metres of concrete, and 26 kms of motorable roads. It took more than 1,300 workers and 300 engineers over a decade to bring the project to fruition.

The bridge, on the upstream of Salal Dam, is situated near Kauri village in the Reasi district of Jammu & Kashmir. It is part of the Udhampur-Srinagar-Baramulla Rail Link Project (USBRL) that will connect Jammu & Kashmir with the rest of the country. “We have built the bridge over one of the deepest gorges in India with treacherous mountain slopes and unpredictable rock strata. Stabilising these steep slopes in an earthquake prone area was a monumental task,” said Giridhar Rajagopalan, Deputy Managing Director, Afcons.

This bridge is one of its kind with an arch span of 467m and a deck length of 780.3m, weighing more than 8,498 tonnes. An incremental launching technique was used from both sides of the bridge, from the Kauri and Bakkal ends. “We employed controlled blasting techniques to carve space on these slopes and then undertook extensive foundation work involving over 34,000 cubic meters of concrete and 5,800 tonnes of reinforcement”, he added.

The real challenge was creating a stable foundation for the world’s highest single-arch railway arch in an area that is both geologically unstable and seismically active. In such a scenario, every step—from slope stability analysis using DIP & SWEDE software, to massive consolidation grouting and installation of rock and cable anchors—had to be executed with extreme precision. “Simply put, nature gave us a fierce battleground, and we had to respond with equally fierce engineering ingenuity”, he continued.

The arch closure of the bridge was the most challenging and required extreme precision. Afcons created a virtual twin of the bridge using cutting-edge software to ensure precision in stress distribution, component intricacies and camber requirements. They deployed the world’s tallest crossbar cable crane across the gorge—a technological marvel in itself—which allowed them to handle and place very heavy steel segments with extreme precision.

Some highlights include establishing a state-of-the-art fabrication facility on both sides of the gorge for enabling on-site fabrication of arch and deck components, employing plasma cutting precision machines taking CNC inputs directly from the design files and employing phased array ultrasonic testing (PAUT) for the first time for ensuring strict quality control on site.

“In addition, for the first time, we provided double corrosion protection (DCP) DYWIDAG anchor cables capacity of up to 120 tonnes for ensuring stable slopes under the massive arch foundations. We used innovating incremental launching techniques on the transition curve of the deck on the completed arch and for the very first time for the Indian Railways, a lab accredited by the National Accreditation Board for Testing and Calibration (NABL) was established at the project site”, said Rajagopalan.

The bridge was designed for blast load in consultation with the Defence Research and Development Organisation (DRDO), marking a first in India. Even if one critical member of the arch is removed, the bridge will still be able to carry traffic at restricted speed and even after the removal of one pier, the bridge will not collapse under self-weight.

The first major milestone came with the arch closure on April 5, 2021. It marked a historic milestone, when the final segment was clinically placed to complete the enormous steel arch. The second landmark was realised with the completion of the Golden Joint on August 13, 2022. This marked a historic milestone in completing the world’s highest single-arch railway bridge. Through incremental launching from both the Kauri and Bakkal sides, a remarkable feat was accomplished — the connection of the deck.

Safety was non-negotiable throughout the project. The project team maintained an unwavering focus on safety and an uncompromising commitment to quality. State-of-the-art technologies were harnessed and meticulous inspection and testing procedures were executed. The project team adhered to the highest international safety standards.

The Bridge is located in a region prone to high seismic activity, extreme temperature fluctuations, and high wind velocities. To ensure structural integrity, the bridge is designed to withstand high wind speed up to 266 Km/Hour and to bear earthquake forces of highest intensity zone-V in India. “Moreover, we carefully considered security challenges, including potential threats. Its design thoughtfully incorporates contingency measures, ensuring minimal impact and continued operation, even in rare instances of adversity”.

The Chenab Railway Bridge is not just an infrastructure project but also a transformational one. It is intricately woven into the lives of local communities. The project ignited economic growth and created job opportunities. Locals were inspired and eagerly joined the construction, aided by training programmes offered by the project. It uplifted the quality of life, fuelled businesses and in the future is expected to spur tourism.

This project showcases the strength of collaboration, innovation, and determination. The Indian Railways and Afcons are proud of this remarkable engineering masterpiece that has firmly established India on the world stage. The design life of the bridge is 120 years.