Building demolition explained

Modern building demolition is an exquisitely choreographed dance of destruction. Dynamite-triggered ‘implosions’ – where a building collapses in on itself just like a crumbling house of cards – are so violently beautiful that they have even become a spectator sport. Demolition junkies are known to camouflage themselves as shrubs just to get a closeup shot of the carnage.

Blowing up a building is easy, minimising damage to nearby structures is the tricky part. There are tumbling walls and flying debris to worry about, not to mention the earthquake-like vibrations produced by millions of tons of crashing cement and steel. The explosives alone can produce high-pressure shockwaves that shatter windows for miles.

Demolition experts are called blasters (‘explosives engineer’ lacks a certain punch). They know that the most powerful force on a demolition site isn’t the thousands of pounds of dynamite, but the incredible potential energy of gravity. The key to minimising damage and softening the impact of 30 stories of rubble is to use the least amount of explosives possible and let gravity pull the building down in a progressive, ‘liquid’ collapse.

To trigger a progressive collapse, blasters divide the building into separate vertical columns. They drill thousands of holes in the weight-bearing supports under each column and stuff them with dynamite. The supports are wrapped tightly in chain-link fencing and thick plastic fabric to contain flying debris.

Each stick of dynamite is plugged with a blasting cap that controls the precise timing of the explosion. All of the explosives are connected back to a single detonator by miles of detonator cable. When the blaster yells “Fire in the hole!” he activates the detonator, initiating a series of sharp, popping explosions that obliterate the column supports section by section.

The result is breathtaking. Each column seems to melt to the Earth in a smooth, wave-like motion. The fluid collapse sequence minimises vibrations on the ground and the small, delayed explosions reduce the damaging effects of shockwaves. When the dust settles (which can take 15 to 30 minutes), all that is left is a two-storey pile of rubble, neatly contained within the footprint of the original structure.