Delhi Metro Constructs bridge with 100 metre long Span at Okhla Over Indian Railways Tracks

The Delhi Metro has constructed a bridge with a hundred metre long span at Okhla over the Indian Railways tracks on the Central Secretariat – Badarpur corridor. The bridge is a major engineering landmark as it has been constructed without hampering the railway traffic below.

The main details of this bridge are:

• This is the longest span ever built by the DMRC. Earlier, the Delhi Metro had constructed a bridge over the Indian Railways lines near Pragati Maidan, where the length of the main span was 93 metres.

• The DMRC had to use such a long span over the Northern Railways track as four Indian Railways lines are passing below the bridge. The bridge, which is located between the Okhla and Jasola Metro stations, has a total length of 250 metres and is divided into three spans. While the middle span is of 100 metres, the other two spans on the sides are of 75 metres each.

• The Delhi Metro has employed the ‘Balanced Cantilever Construction methodology (BCLC)’ for its construction so that the rail traffic below the Metro corridor is not hampered. This technique employs the use of a bridge builder that constructs the bridge segment by segment at a time.

• This bridge has been built using M-60 grade concrete and about 130 workers were engaged in the construction of the bridge on a daily basis.

• The construction of this bridge was difficult since the bridge was built on a very sharp curve with a 300 metre radius and the installation of the individual segments of the bridge on the curve was difficult as the rail traffic moving below could not be obstructed during the construction.

• The heavy works such as gantry movement were done under traffic blocks on railway tracks. Since the bridge balance was always in a see-saw condition, engineers had to maintain strict construction sequence. Additional temporary supports were designed for added safety.  Engineers monitored the stresses and strains in these temporary supports as well as inclination and tilt in the super structure of the bridge at every stage of construction.

• Visual electronic indicators were also installed with the help of Japanese scientists and the Japan International Cooperation Agency.  Japanese consultants on DMRC works interpreted all monitoring data regularly and kept designers in the loop. Strict survey control and monitoring could ensure a safe construction with perfect alignment.

• The existing railway tracks below this bridge link New Delhi with Agra, Mathura on Mumbai main line and then to other parts of the country and therefore is a very important railway stretch.