The nine-year saga leading up to the demolition of the Supertech twin towers is all set to culminate on Sunday at 2.30 pm. The demolition of the Apex (32 storeys) and Ceyane (29 storeys) towers would leave behind approximately 35,000 cubic metres of debris that would take at least three months to be cleared.
The nearly 100-metre-tall structure, taller than the Qutub Minar, will be safely pulled down.
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Edifice partner Utkarsh Mehta told PTI that they are "150 per cent" confident that the towers will come down safely and in the direction as envisaged by them, assuring residents of no damage to their homes except for chances of "cosmetic cracks" on outer paint and plasters of some structures.
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On how many options they had for demolition of the twin towers, Mehta said there are basically three techniques to safely raze down any structure of such a scale - diamond cutter, use of robots and implosion.
"The technique is chosen on the basis of three parameters - cost, time and safety," he said.
He said the 'diamond cutter' would have taken over two years of time to completely demolish the twin towers safely, and its cost would have been five times of the implosion method.
"There we would have to slowly cut down every column, wall and beam from top to bottom using cranes," Mehta said.
On using robotics, he said this technique would have caused a lot of noise over a period of 1.5 years to two years and disturbed the residents of nearby Emerald Court and ATS Village.
"Its cost would have been less than the diamond cutter technique but more than implosion," he said.
The Edifice boss said since the Supreme Court had also ordered that this project should be done in the shortest possible time and with no disturbance to neighbouring residents, the implosion technique became the choice for the project.
"As Edifice and our South African expert partner Jet Demolitions also had precedence and experience from the demolition of Maradu complexes in Kochi, Kerala, we decided to go ahead accordingly," he added.
The twin towers are being demolished in pursuance of a Supreme Court order of August 2021 that found their construction within the Emerald Court society premises in violation of norms.
Over 5,000 residents of Emerald Court and ATS Village - the two closest societies to the twin towers - will be evacuated on Sunday by 7 am. Some 2,700 of their vehicles will also be removed from the premises and the residents will have to take away their pets too with them.
An exclusion zone will be created in a radius of up to 500 metres around the twin towers where no human or animal would be allowed except for a team of Indian and foreign blasters engaged in the demolition.
Over 3,700 kg explosives are being used to implode the Apex and the Ceyane towers, leaving behind an estimated 55,000 tonnes to 80,000 tonnes of debris which would take at least three months to be cleared from the site.
While demolition projects by themselves are not very uncommon in India, the demolition of buildings in question is unique owing to their height and being built on shear walls, as opposed to usually being built on columns.
The buildings, therefore, are a lot stronger, built using more steel and, hence, posed a bigger challenge to the demolition company in-charge of flattening these buildings, according to Anand Sharma, Director of Exiqude Private Ltd and a consultant in this project. He added that for drilling holes to place explosives in the buildings, having numerous shear walls was a disadvantage as they have a greater width and so, one would need to drill deeper holes.
The challenges, however, did little to deter authorities from choosing the method of controlled implosion to accomplish the demolition. This is because there were various factors facilitating the use of this method.
Terming it an "effective method for high-rise buildings", Sudip Paul, General Manager, Structural Engineering, Engineers India Ltd, a veteran in the area, said there are lesser disturbances to the neighbourhood and traffic and other routine activities.
"Because this is a quick process compared to conventional dismantling, there is decreased exposure of the working personnel to the dismantled debris, dust, noise and vibrations arising from the blasts," he noted. Additionally, the dismantled debris is expected to fall within the footprint of the buildings and, thus, is an added advantage, owing to the density of the locality where these buildings are situated.
However, the method is not without its fair share of inadequacies.
According to another structural engineer, a Senior Manager with EIL, Amresh Kumar, "A poorly executed implosion may cause debris to fly out at a very high speed and can be a threat to other humans."
"It could also cause partial demolition, in which case, the building may collapse sideways and cause damage to other healthy and live structures," he said.
Further, because the behaviour of the structure is now unknown, the structure may be rendered unfit for further implosions.
Paul adds that this partial structure then becomes a constant source of dust or debris, causing pollution and health hazards and presents a challenging working environment, should a next stage demolition be envisaged for the partial structure.
The explosives are placed at beam-wall joint locations in such a manner that when the explosives go off, the beams and walls steadily lose their capacity to sustain their own weights and collapse under the impact of gravity, he said.
On impact to environment, Kumar says, "The dust and debris generated impact the environment adversely and the local pollution control body needs to approve such projects beforehand, and so, they may ask for the mitigation scheme."
(With inputs from PTI)
