With the countdown having started for the Commonwealth Games 2010, Delhi Metro’s express link to the airport is fast nearing completion. To expedite the process and make it more cost effective, Delhi Metro Rail Corporation (DMRC) is making use of gigantic 25 metre-long girders to join spans on elevated stretch of the section.

The technique is being used for the first time in India. Earlier it was used only in China and Taipei. Delhi Airport Express Line, which is scheduled for a October 2010 opening, has to be constructed on a very tight deadline. So, DMRC officials decided to use the large girders, each weighing about 120 tonnes, in place of segmental construction technique. Till now, the concrete spans between two pillars on which the tracks are laid were made of 12 small segments, which were joined together with metal cables and stressed. But now, DMRC is going to have two gigantic concrete slabs of 25 metres length, which will be placed side-by-side on top of the piers (pillars) to create the foundation of the elevated stretch.

The bigger spans work out to be more economical and also speed up pace of the construction. Officials said it takes about a week to join the space between two pillars using segmental construction while the bigger spans can be put in place in just one day. ‘‘The cost of construction with the existing 3-meter spans works out to Rs 24 crore per km, while the 25-meter ones cost Rs 19 crore per km. So using the bigger spans will result in a saving of nearly Rs 5 crore per km,’’ said a DMRC official.

With so many benefits, why is the technique not used for construction of all stretches? DMRC officials explain that it can be used only in areas where there is enough space near the construction site. This is because the concrete girders are made at a casting yard and transported to the construction site on specially designed trailer trucks which are 35m long and have 64 tyres.

The Mumbai Metro also wanted to make use of the long girders but transporting them on narrow Mumbai roads would have been impossible, so the idea was dropped. The elevated stretch of the Airport Express Line in the Capital falls between Buddha Jayanti Park and Mahipalpur which has wide roads. A total of 504 such girders are being used on the 7-km stretch, of which 22 have already been launched.

IGI line Progress

• Length - 22.7 km (7 km elevated)
• Number of stations - 6 New Delhi Railway Station, Shivaji Terminus, Dhaula Kuan, NH-8, IGI Airport and Dwarka sector 21
• Max train speed - 135 kmph
• Frequency - 10 mins in 2010; 6 mins by 2021
• Completion deadline - July 2010
• Journey time from CP to IGI - 18 minutes
• Journey time to Dwarka - 24 minutes
• Expected ridership - 46,500 in 2011; 86,000 in 2021
• Estimated cost - Rs 4,000 crore (approx)
• Total number of special large girders being used - 504
• Length of girders - 25m FEATURES
• Maximum fare - Rs 150 (up to IGI),Rs 30 (IGI to Dwarka)
• Business Model - Public-private partnership (PPP) with DMRC developing the civil structures and later playing the watchdog for 30 years

Some of the features at the Airport Express Link stations:

• Baggage check in facility at New Delhi Railway Station and Shivaji Stadium
• Lifts at all stations will be wide enough to accommodate passengers with luggage
• Parking available at Shivaji Stadium and New Delhi stations. Multi-level parking facility to come up at New Delhi station

Source: Times of India