Yesterday morning a crowd in Christchurch watched from a safe distance as a 14 storey building was demolished in just 10 seconds by implosion. It fell sideways a little then collapsed into a heap of rubble, with a large cloud of dust. A 6-year old boy who has cancer pressed the button which started the collapse. The winner of a Trade Me auction paid $26,000 for the chance to press the button but gave that chance to the Child Cancer Foundation.
Inside the building were 47.5 kg of explosives. Twelve men spent a week drilling holes in the concrete support columns for the explosives. Most of these were placed in the ground floor, but also in the second, fifth and ninth floors. It cost the insurance company $1 million to demolish the building this way, slightly less than the usual demolition method.
This is the first time implosion has been used in New Zealand. Not every building is suitable for this method of demolition. There must be no other buildings nearby and it must be safe enough for workers to enter to place the explosives. Now that so many buildings have already gone in the Christchurch CBD, this method may be suitable for other buildings.
implosion – collapsing inwards
rubble – broken concrete etc.
column – like a tube or cylinder of concrete, supporting the floors above