H. C. Kunwar
The world’s tallest rail bridge over Chenab River in Reasi district being constructed by Konkan Railway Corporation Limited (KRCL), a Central Public Sector Enterprise under the Ministry of Railways, is likely to be ready by 2016. This bridge will be on the Udhampur – Srinagar – Baramulla Rail Link (USBRL) project which is a national project to provide rail connectivity to the beautiful valley of Kashmir. Konkan Railway has taken up the construction of part of USBRL project from Katra to Dharam in December 2002. Chenab Bridge, perhaps the most challenging project, is to be built at the height of 359 metres (height of Qutab Minar is 72 metres and of Eiffel Tower is 324 metres). Chenab Bridge is having the central span of 457 metres. When constructed this bridge will qualify for world record for being the tallest rail bridge from the river bed. Currently the world’s tallest rail bridge is located over France’s Tam River with its tallest pillar rising 340 metres, with the actual height where the train runs on the bridge being 300 metres. The design of bridge also takes care of blast load, which is internationally an unique feature. The painting scheme for this bridge is designed for 35 years of service life so that during service life of 120 years, only 3 times repainting will have to be done.
For construction of Arch portion of the bridge over the river, a novel method of construction using the cable car is designed and under construction. This cable car runs on 54mm cables laid across the river valley and connected through 127 metre high pylons (towers) on either side of river. The consumption of structural steel for this project is very huge. The construction of Chenab Bridge will comprises of earthwork in excavation for construction of foundations, over 46,000cum of concreting, 3600 tonnes of reinforcement steel and 25,000 tonnes of structural steel (an equivalent to volume of a 54 story building on a football ground size plot). Fabrication of the steel structures involves very high degree of precision and quality wielding using latest wielding technologies.
Construction of Railway Bridge over river Chenab bridging steep banks on Bakkal (Katra) and Kauri (Srinagar) ends respectively, without causing any hindrance to the water flow is a challenge. Approach roads measuring a total length of about 5 kilometres are being constructed in very difficult terrain to reach to main span foundations. To ensure stability of the foundation cut profiles, the slopes have been suitably designed and will be protected by means of rock bolting and shotcreting. From Katra side, the railway line comes out of 5.9 kilometre long tunnel and after moving over other bridges comes to a station called Salai-A and after moving over Chenab bridge comes to a halt station called Salai-B. These two stations are meant to serve the local population of either side of the river.
The bridge is designed for 266 kmph of wind velocity and wind tunnel simulation test for the same was conducted in Denmark. However, trains will not be permitted to travel over the bridge when wind velocity exceeds 90 kmph. Suitable instrumentation like anemometers for measuring wind velocity, accelerometers for measuring ground acceleration in the event of an earthquake, temperature monitor etc., will be installed at critical locations to generate alarm to the adjacent stations in case of danger. Various geotechnical investigations are carried out for this bridge like soil boring done along the alignment of the bridge, plate load test and shear load test conducted inside drift (a tunnel like cavity made for investigation) at foundation level of Arch.
The section from Katra to Dharam being constructed by Konkan Railway is 70 kilometres in length. It comprises of 59.457 kilometres (85%) of route in tunnels, 6.6 kilometres (9%) of route on bridges and balance 6% of route in cutting and embankments. To make access to these sites, Konkan Railway has to make 166 kilometres of project roads including road tunnels and many temporary Bailey bridges.
The work was pended in July 2008 for review of alignment and after review works were restarted in September 2009. At present, Final Location Survey for 28 km is in progress taking into account changed ruling gradient of 1 in 80. The target for completion of project is December 2017. To expeditiously execute the project Konkan Railway has set up Project Head Office at Jammu. Its project camps are located at Reasi, Kauri, Dugga and Sangaldhan. KRCL has mobilized a team of about 240 staff and engineers for taking this project ahead. The construction machinery, plant, equipments, materials, technicians, skilled and un-skilled manpower is arranged by KRCL’s construction contractors. For design support, various National and International agencies have been engaged. The construction of 166 km of approach/feeder roads through this inaccessible terrain is a challenging job to take up the railway construction works.
Konkan Railway has the experience of construction of 740 km of Railway route length between Roha to Thokur (near Mangalore). This route has 91 tunnels aggregating to 85 km, with Karbude tunnel of 6.5 km which is the longest transport tunnel in the country. Over Konkan Railway route 179 major bridges aggregating to 19.8 km of bridge length have been constructed. The longest bridge is across Sharavati river which is more than 2 km long.
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