Given the fevered pace of China’s infrastructure development, 16 years is ancient. That’s why the two-lane concrete Zhuan-yang viaduct running through central China, had to go — a bigger and better six-lane freeway was in the works. But to demolish the original roadway without harming the surrounding homes, engineers smothered the blast under a blanket.
The surrounding neighbourhood tightly packed in around the viaduct wasn’t the only concern for engineers in determining how to best bring down the structure — major, 100,000V power transmission lines, 30 local gas lines and the main national East-West gas pipeline ran underground parallel to the road as well. One misplaced stick of dynamite would sever power and light the area up like a giant Bunsen burner.
To prevent collateral damage along the 3.5km bridge — the longest reinforced concrete bridge demolition project ever attempted in China — engineers swaddled the Zhuan-yang viaduct with a cloth wrapper, secured it with wire then reinforced the covering with large water-filled bladders and sandbags. This wrapping prevented hunks of viaduct from exploding through surrounding homes and kept dust to a minimum as the structure fell, while the sandbags and bladders absorbed and dampened some of the blast’s energy and noise.