The central government inaugurated the much-awaited six-lane cable-stayed Chambal bridge in Kota, Rajasthan, on August 29, 2017. The completion of the bridge, which had been under development for the past 12 years, concludes the work on the 3,300 km East-West Corridor (of the Golden Quadrilateral), which connects 14 national highways passing through seven states and 28 key cities across the country. As an alligator sanctuary falls under the bridge over the Chambal river, a 700 metre stretch of the bridge has been suspended with cables, thus giving it the name the “hanging bridge”.
All about the masterpiece
Funded by the National Highways Authority of India (NHAI), the project entailed an investment of Rs 2,007 million per km, amounting to a total of Rs 2.8 billion. The contract for the project was awarded to the Hyundai Engineering and Construction Corporation Limited (HDEC) and Gammon India Limited joint venture. The Louis Berger Group and COWI India Private Limited were the supervision consultants for the project.
The bridge has innovative design features which are environment- and wildlife-friendly. The cable-stay portion was made in a semi-fan arrangement. It has a main span of 350 metres and two side spans of 175 metres each. The bridge has a six-lane vehicular deck, three for each direction. A 400 metre access bridge and a 300 metre approach road are also a part of the project. It is constructed over a deep channel with a constant water depth of 20-34 metres and a waterway of 250-300 metres. About 34,665 cubic metres of concrete and 3,568 metric tonnes of steel have been used in the construction of this bridge.
- Foundation: The lateral piers of the bridge are supported by rectangular footings, resting on safe rock. The foundation of the pylon piers comprises two vertical shafts of 4.5 metre diameter each, and a maximum length of 15 metres. For the shaft design, friction and end bearing piles were used to reduce the differential settlement to an acceptable level.
- Pylons: The pylons are 80 metres high with a constant width of 3 metres, and a variable length of 4 metres to 7 metres. The pylons contain a steel frame in which there are passive anchorages of stay cables. This steel frame is composed of 20 steel boxes.
- Stay cables: The stay cables are composed of individually sheathed strands with triple protection – galvanisation, wax filling and individual polyethylene sheaths. Anti-vibration devices have been provided for the longer stay cables.
- Deck: The concrete deck of M60 grade is prestressed longitudinally using internal and external tendons, and transversally using only internal tendons.
An instrumentation system has been installed on the bridge to inform the control room about traffic, rain, cyclones and earthquakes.
The journey to becoming a reality
The construction of the bridge was fraught with several challenges, a result of the complex engineering features of the project. Though work began in 2006, it had to be halted for five years after one of the pillars collapsed in December 2009, killing at least 48 people.
The project was finally resumed in 2014. However, construction moved at a snail’s pace in the first quarter of the year due to a dispute among the contractors on account of the 2009 incident.
During January-March 2014, NHAI observed that the concessionaires failed to make any progress on 15 out of the 18 work items committed for completion. Meanwhile, the remaining three items reported a physical progress of less than 50 per cent . NHAI’s intervention resulted in an agreement between the two companies and work on the bridge was finally completed in 2017.
The project involved the construction of a 1.4 km cable-stayed bridge with a width of 30 metres over the Chambal river on National Highway (NH)-76 in Rajasthan. The bridge will connect the Kota bypass from km 381 to km 406 on one side and the four-laned Kota-Chittorgarh section from km 361 to km 381 on the other. It was implemented under Phase II of the National Highways Development Programme on an engineering, procurement and construction basis.
Benefits in store
The bridge will enable heavy vehicles to bypass Kota city, thus curbing pollution and traffic congestion. It will also accelerate development and thereby contribute to employment generation. The bridge is also expected to reduce the commute on the Kota-Chittor section of NH-27 and the Kota-Jhalawar section of NH-12 by one hour. The Chambal river bridge is the fifth cable-stayed bridge in the country. Though delayed, its commissioning will certainly present a strong case for the construction of such bridges in other parts of the country to improve connectivity.