Railway bridges: The engineering that connected India
A history of innovation in building some of the largest and finest bridges on the Indian terrain
By Heritage Directorate, Indian Railways
Vinoo N Mathur
After the first Indian rail line became operational in 1853, the network expanded at a furious pace. By 1920, there were over 62,000 kilometres of rail lines in the then-British India - which included the present Pakistan, Bangladesh and Burma. The engineers and labourers who built this impressive network overcame many obstacles, but the major challenge they faced was fording its many large rivers.
A bridge across the GodavariHeritage Directorate, Indian Railways
The rivers in India were much wider than rivers encountered in Britain and elsewhere in the world.
They were also constantly shifting course, and had very significant seasonal variation in the flow of water. With centuries of accumulated silt in the alluvial soil, it was hard to find rock or suitable strata on which to build bridge foundations.
The early engineers were thus pioneers and great innovators, possessing remarkable perseverance and organisational skills. They built some of the largest and finest bridges in the world which, in many cases, are still in use more than a century and a half later.
The Arch bridge
A number of designs were adopted for the railway bridges. One of the earliest was the time tested Arch Bridge, which had been mastered by the Romans. The arch bridge transfers the vertical weight of the bridge and the load on it to a horizontal thrust along the curve of the arch, and finally to the abutments on both sides. A remarkable use of the arch is in the Gallery Arch bridges on the Narrow Gauge line from Kalka to Shimla, where tier on tier of arches were built in the style of the ancient Roman aqueducts, to carry the line from one spur to another.
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The narrow gauge track of the Kalka Shimla line. The track is laid on top of the multi- tier gallery arch bridge.
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The first level of the multi tier gallery arch bridge on the Kalka Shimla line.
Meter Gauge viaduct on the Quilon-Tenkasi lineHeritage Directorate, Indian Railways
Though the arch bridges continued to be built till the beginnin of the 20th century, they faced a few costraints. The major one being the limited capacity to manufacture bricks for the bridges and non-availability of suitable clay for brick making near the bridge sites. Therefore, engineers began to design bridges early with steel girders ordered from Britain.
The iconic Flying Rani crossing the Vasai bridgeHeritage Directorate, Indian Railways
The Screw Pile bridge
The Screw Pile bridge was another type of bridge the early engineers
adopted, particularly while bridging estuaries, backwaters and where the
current was not severe. The piers would consist of two or more cast iron piers that would be
screwed down to an appropriate depth below the silt, mud and sand where a
stratum of hard clay was found. However, the screw pile design had its own limitations and as policy, the government decided to replace all bridges of this type following an accident in 2001.
The original Vasai Creek bridge - opened in 1864 - was one of the earliest examples of the screw pile bridge. It consisted of piers of three piles that were 2 feet 6 inches in diameter, and had foundations between 20 and 72 feet below bed level. Over these, double spans of 60 feet Warren girders were laid. To strengthen the bridge, two additional piles were added later.
An oddly shaped pier of the Yamuna bridgeHeritage Directorate, Indian Railways
Well Foundation bridge
This method involved sinking cylinders (or wells) of brickwork to considerable depths through the sand, until clay or rock was reached. Then, piers were built over the foundations of a single well or a cluster of wells. For the bridge over the Yamuna at Allahabad, each pier is founded over a cluster of 12 wells, and they rest on strong iron curbs.
Due to the difficult subsoil conditions, open foundations could not be applied in India in most cases. The Well Foundation design has therefore been a major contribution to large bridge construction in the country.
Its evolution was pioneered by the early railway bridge designers and builders, as its advantages were quickly realized. The design was indigenous to India and had been adopted in early bridge and building construction, apart from the construction of ordinary wells for drawing water.
The third bridge across the GodavariHeritage Directorate, Indian Railways
Once the wells were founded they were usually filled with sand and capped. The well foundation over time has become the most popular method of founding bridges in India particularly where scour and bearing capacity are considerations.
They have the capacity to efficiently take on very large vertical and horizontal loads. It is only relatively recently that bridge engineers have begun to consider pile foundations as an alternative methodology based on time and cost considerations.
The new Beas bridgeHeritage Directorate, Indian Railways
The super-structure normally consisted of iron or steel girders. In the early days lattice girders were sometimes used.
Some examples of this are the original girders on the Yamuna Bridge at Delhi, the RMR-built bridge built over the Yamuna at Agra, and bridges on the Beas and Sutlej Rivers on the line from Delhi to Lahore, are of lattice design.
On the Allahabad Yamuna Bridge in 1913, down-line girders were provided to facilitate double-line working which were 'Pony deck Span hog backed N trusses', with railway on top and roadway underneath for cart traffic.
The need for constant river training and protection works is integral to the construction and maintenance of bridges particularly in Northern and Eastern India. With a view to protect the bridge, ensure the river flows through a well defined channel and check the effects of meandering, various types of river training works have had to be carried out. These include construction of Guide Bunds, Groynes as well as Marginal and Closure Bunds. In the case of the new Brahmaputra Bridge at Dibrugarh, currently under construction, Guide Bunds have been built on the North and South Bank 2 kms. and 2.7 kms. long respectively, apart from about 16 km long dykes on each bank.
Steel Arch bridge
The tallest steel arch bridge in the world, with a height of 359 meters from the bed level to the centre of the arch, is being constructed on the line from Jammu to Srinagar across the Chenab. In creating these masterpieces, engineers and construction workers have toiled tirelessly, little realizing their tremendous contribution in building India's massive rail network that integrates diverse regions, people and cultures into a formidable and united nation.
Railway Bridges are some of the 'Mega Structures' that have been created by railway engineers over the last hundred and sixty years. The East India Railway engineers in the 1850's had the vision and foresight to build the substructure of most of their bridges for double line and many of them continue to serve the system today despite the increase in axle loads.
The Jubilee bridgeHeritage Directorate, Indian Railways
Thanks to the perseverence, skill and dedication of the engineers, both pre and post independence, by the time the British left India, the rail network had reached almost every corner of the nation.
