Van Eck House, a 20-storey skyscraper built in 1937, was for many years the tallest building in South Africa, standing out on the skyline of Johannesburg. In 1983 it was demolished in 16 seconds.
Although it stood in the densely built-up city centre, no damage was done to any other building — even plate-glass show-room windows on the other side of the street were unharmed.
Dropping a building so that every piece of rubble falls within its own walls is called `implosion’ by Mike Perkin, the explosives engineer of Wreckers (Pty) Ltd who carried out the feat. His first task was to study the structure of the building and assess its condition. He was then able to plan how to place explosive charges that would destroy vital points of structural support.
Before the blast came two months of preparation. Internal partitions were re-moved, together with any other non-structural parts of the building that might obstruct it from falling freely. Protective sheeting was placed around the building to stop debris flying out. It was also necessary to make sure that the vibrations, caused by the explosions and the building crashing to the ground, would not damage surrounding buildings. Perkin timed the explosions so that the rubble from the first blasts at the bottom of the building cushioned the fall of the remaining material.
His team drilled nearly 2000 holes between 4 and 30in (100 and 760mm) deep to take the charges, and laid 6 miles (10km) of wiring. Most of the charges were placed in groups of five holes drilled into wails or supporting columns. On every floor 50 charges were needed for the walls of the lift shaft and 60 charges for the walls of an interior well. The charges in the columns were twice the size of those for demolishing the less robust walls.
The charges were fired electrically. The series of explosions started when Perkin pushed down the plunger, sending current to the detonators — caps of high explosive placed in every cartridge. They exploded either at once or after a set delay, sending a ripple of blasts through all 20 storeys of the building.
Picture Credit : Google