With the concept of skyscrapers fairly recent in the country, it has little expertise or research in demolition of such buildings, according to experts. Supertech’s plan was to build 40 floors each in Apex and Ceyane, out of which 32 have been constructed till now. The demolition will present a stiff logistical challenge because of buildings in the vicinity. The closest, a neighbouring building in the same Emerald Court compound, is separated by a narrow driveway from the walls of the twin towers.
Though there are various techniques for demolition of such tall structures from top to bottom or vice versa, experts said implosion is the preferred method for densely populated areas. In this technique, small explosive devices are placed at multiple locations in the building in such a manner that when detonated, the debris falls within the premises. While such demolitions have been done worldwide, and on a smaller scale in India as well, it requires much preparation. Additionally, in the case of the twin towers, preserving the structural integrity of the neighbouring towers within Emerald Court will be a challenge.
“There is hardly any example of skyscraper demolition or related research in India and the Noida Authority will need to hire foreign consultants as experts. So far, implosion is the technique used successfully everywhere,” said Divya Kush, president of Indian Institute of Architects.
The closest such demolition was that of four multi-storeyed complexes in Maradu, Kerala, in January 2020. The razing of these buildings was also ordered by the Supreme Court as they were constructed in violation of zoning regulations. The tallest building among these had 18 floors.
Experts involved in the Maradu demolition said survey and preparation takes the maximum time, since the placement of explosives has to be accurate in order to prevent any damage to buildings in the vicinity. Anand Sharma, director of Rajasthan-based firm Exiqude Pvt Ltd that led the demolition of the two towers of Alpha Serene, one of the Maradu complexes, said, “The blast needs to be planned and designed perfectly. We select the floors to be blasted, remove the support and walls from these floors and place the explosives in such a manner that the pillars blast in a sequence, one after the other.”
He added that the closest inhabited building in Maradu was about 8m away, while the closest in Noida is Aster-2 tower of Emerald Court, about 9 metres away. “There are several factors to consider, which is why the logistics and cost cannot be calculated before a thorough survey of the area,” added Sharma.
“The blasts have to be conducted in an extremely controlled manner. The intensity of the blast will depend on the height of the building, total area, dead weight, floor load and supporting pillars, among other factors,” said Colonel MK Prasad (retd), a former structural expert with the Indian Army.
Experts said debris from an implosion hardly affects nearby buildings, but dust clouds may remain for a long time depending upon the air flow. “We prefer to evacuate everyone within at least a 50m to 100m radius of the blast in densely populated areas. The dust may remain in the air for 10-15 minutes, but the entire process takes longer. People need to be evacuated for at least 3-4 hours,” said Sharma.
According to Uttkarsh Mehta, a partner from Edifice Engineering that demolished the other buildings in Maradu along with consultants from South Africa, the biggest challenge is to control flying debris to ensure that the building folds inwards like a pack of cards. The entire demolition process in Noida would take over four months from planning to clearing of debris, he estimated.
“In Maradu, it took us about 15 days of planning, two more months of preparing the buildings for the blast, and another month of clearing the debris,” said Mehta.