How explosives will bring down India

BBC News:

In an estimated 12 seconds, two skyscrapers near the Indian capital, Delhi, will be demolished by implosion on Sunday afternoon.

The two cheek-by-jowl towers called Apex and Ceyane – which were built by a private developer called Supertech and later found to be in violation of building norms – will be the country’s largest skyscrapers ever to be imploded.

The ‘Twin Towers”, as they are rather curiously called by the media, rise to more than 320ft (97m) and 30 storeys in a densely populated neighbourhood in the city of Noida.

Some 3,700kg of explosives will power the implosion – getting an edifice to collapse on to itself – in what will be a highly skilled job involving engineers from at least three countries. One engineer has called it a “beautiful feat of engineering”.

• How do you demolish a skyscraper?

Such demolitions are generally not permitted or are rare in densely built areas around the world. That makes Sunday’s demolitions especially challenging.

Consider this. A 12-storey inhabited building stands barely 30ft (9m) from the two towers. Some 7,000 people live in some 45 condominium buildings on either side of the towers.

All humans and pets in these buildings will have to evacuate early on Sunday morning. They will only be allowed to return to their homes five hours after the implosion. Stray animals will be scooped off the streets and put in animal homes. Traffic in the area and on a key expressway will be halted. The implosion is likely to generate a cloud of dust rising to 984ft (300m) from the ground, so airports and the air force have been told to ensure safety of flights.

That’s not all.

Some 50ft (15m) from the demolition site is an underground pipeline which supplies cooking gas to Delhi.

People living in the neighbouring buildings have expressed worries that the vibrations from the implosion could damage their structures.

But engineers involved with the demolition say there’s nothing to worry about.

Buildings in Noida are designed to withstand earthquakes. British engineers who are helping with the demolition have calculated that the blast will trigger vibrations which will be a tenth of a quake measuring four on the Richter scale. Also, the basements of the “Twin Towers” will be stuffed with loose debris to absorb the vibrations.

“It’s all safe,” says Mayur Mehta, a senior engineer at the site.

On Sunday, six people, including three men in charge of the explosion – also called “blasters” – and a police officer will be allowed inside what authorities call an “exclusion zone” to set off the explosions, which will see the towers implode simultaneously.