John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.
The explosive takedown of Wuham's 2.2-mile long viaduct was the longest concrete-bridge demolition in China's history.
How do you explode a 2.2-mile-long bridge in a residential district with no collateral damage?
Very carefully, it turns out – which is obvious when you think about it, but history is full of demolition jobs that somehow go horribly sideways. In the case of the Zhuan-yang viaduct, located in the eastern Chinese city of Wuhan, the repercussions of a botched job were greater than usual. A poorly planned blast could send boulders of concrete through the windows of homes. Or it might rupture one of the many gas lines running beneath the span to create a mushrooming garden of enormous fireballs.
The engineers behind this weekend's behemothic bang-up had a primitive-sounding but effective solution to the bridge problem. They covered the structure with a cloth apron tied tight with wire. They then padded it with sandbags and huge bladders of water. The result was a soft armor that acted like a muffler when the bridge was finally blown, soaking up rubble and dust and preventing the billowing debris cloud that's followed some other lung-clogging demolitions.
The night explosion was the longest concrete-bridge demolition in China's history, according to ITV News. In a sign of how fast China is developing, the two-lane bridge, which was only about 16 years old, will soon be replaced with a six-lane highway that'll be a mile longer than the original. (For more images of the busted bridge, which fell in less than 20 seconds, check out the slideshow at China.org.)
Top photo by Reuters/Darley Shen