The Hindu : Front Page : An extraordinary new accomplishment by Delhi Metro now

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Thursday, Sep 14, 2006
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An extraordinary new accomplishment by Delhi Metro now

Gaurav Vivek Bhatnagar

INDIA'S FIRST, WORLD'S SECOND: A train runs under the new Delhi Metro railway bridge, built over five lines of the Indian Railways, near Pragati Maidan on Wednesday. PHOTO: V.V. KRISHNAN

NEW DELHI: By building India's first "extra-dosed" bridge near the Capital's Pragati Maidan -- also only the second of its kind to be built over a railway crossing anywhere in the world - the Delhi Metro Rail Corporation has accomplished one more technological innovation.

Part of the upcoming new Barakhamba Road-Indraprastha section on Line 3 of the Delhi Metro railway network, the bridge has been built using a special technique since it has a 302-metre radius curvature and is 93 metres long.

According to the DMRC authorities, the construction of the extra-dosed bridge was a very complex affair as it had to be built over five very busy lines of the Indian Railways. With nearly 200 trains, including many major trains going towards western and eastern India, passing on the tracks below the new bridge day in and day out, it had to be constructed without any disruption to the train movement.

Also, since no pier could be put between the train tracks, the main span of the extra-dosed bridge over the railway crossing -- which was 93 metres long -- has no piers to support it. The main span was also kept long to allow for future expansion of the Indian Railways lines.

As the DMRC authorities don't tire of mentioning repeatedly, this is only the second bridge of its kind built over a railway crossing in the world, the first being in Japan. Also, at present there are only 26 extra-dosed bridges in the world, of which 15 are in Japan.

The construction of the extra-dosed bridge in Delhi started in February this year and now it is almost complete. As many as 10 DMRC engineers and more than 230 workers were involved in the construction, which was carried out in the most trying circumstances. Special care had to be taken of the overhead electric lines of the Indian Railways during the construction of the bridge.

All the critical work over the tracks was done at night. Stringent safety precautions were maintained at all times and no accident took place during the construction. Protection nets were placed below the working platform to prevent any mishap. Other safety precautions included round-the-clock supervision by engineers, earthing of segment launcher, and anchorage of the rear leg of the segments to prevent any mishap. Metro site and design engineers used to be present all night for spot decisions to avoid any delay in the operations.

The design of the extra-dosed bridge was done by a French consultant, Systra, and independently checked by the DMRC. Extra-dosed bridges, according to the DMRC, are the best solution in places where long spans are required to be built and space is limited. Also, they are more economical than the cable bridges while the pylons are almost half in height. The cost of the new bridge constructed by the DMRC, including the design, came to about Rs.6.5 crores.

The Barakhamba Road-Indraprastha section, on which the bridge has come up, is 2.81 km long and is now set to be commissioned by mid-November before the annual India International Trade Fair begins at Pragati Maidan on November 14.

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