Mumbai: Lights, camera, demolish... Lower Parel's Delisle Bridge

The Indian Railways wants to remember the intervening night of February 2 and 3, when it brought down a crucial bridge in the heart of the city and filmed the process — in one of the toughest teardowns in the railways' history.

In a first, the Western Railway documented the Rs 7.5-crore demolition of Lower Parel's Delisle Bridge, which was dismantled between 10 pm Saturday and 8.30 am Sunday.

The authorities intend to use the video to train aspiring engineers in colleges.

"We placed video recorders at vital places on skyscrapers around the bridge to record the entire demolition," said Ravinder Bhakar, Wr's chief public relations officer.

One challenge was the degree of curvature of the bridge, which turns at an angle of 64 degrees above the rail tracks. This made it difficult for the railway workers to know where the centre of mass of the bridge was, and so any wrong move could have tilted the bridge onto the tracks, damaging them.

Also, the bridge was stronger than it seemed.

The officials said its rust was superficial, and internally, the pillars and girders were very sturdy, which made the job tougher.

"This was an unprecedented case. The steel and cement used to construct the bridge had gotten embedded into each other. Usually in such bridges, each piece can be separated. For example, in the early 1990s, a portion of a steel bridge over a railway yard in Howrah was dismantled piecemeal. But this was not possible with Delisle bridge. That is the reason it took so long," said Subodh Jain, former member (engineering) of the Railway Board in Delhi.

The railways normally uses explosives to blast a bridge altogether. But in the case of Delisle Bridge, the authorities had to use over 170 gas cutters to break down the structure into smaller parts and pluck off the pieces using multi-tonne cranes.

"There is no doubt that this structure was one of the toughest to dismantle. But we managed to do it within the deadline," said AK Gupta, general manager, Western Railway.

Railway officials said the idea to video-document came from Andhra Pradesh, where in July 2018 a subway was built in less than 5 hours.