Shock tubes, 7k holes for test blast at Noida twin towers

Officials of Edifice Engineering, the private firm engaged by Supertech to carry out the demolition of two 32-storey buildings situated at Emerald Court project in Noida, said on Tuesday that they will use shock tubes filled with explosives to conduct a test blast at the site. The officials also said that around 300 workers are currently working at the site to drill 7,000 holes of about two metres each in one of the towers for inserting the shock tubes.

The test blast will be conducted in the last week of March or first week of April.

“We will blast five columns, four in the basement and one on the 14th floor, for the test blast using shock tubes. This will be done to check the quality of the concrete used in construction and will help us determine the amount of explosives needed for the two buildings,” said Uttkarsh Mehta, partner, Edifice Engineering.

There are 24 machines being used at the site using water drilling technique to make holes, the officials said.

“We need to drill 14,000 metres or 14km of holes in the entire building. The ground work is on at the site while we arrange the explosives. There is also a lot of water being used up in the process that we are continuously pumping out to prevent it from accumulating inside,” Mehta told HT.

Shock tubes are orange-coloured tubes filled with explosive gel or powder, the officials said.

“Our foreign experts have asked for shock tubes that have 80 grams of explosive powder per metre. As of now, we are getting tubes with 20 grams of explosives per metre. We are in talks with two companies that can provide the specifications we need,” said Mehta.

The twin towers — Apex and Ceyane — in Noida’s Sector 93 will be the tallest structures in the country to be demolished following Supreme Court orders.

Meanwhile, the Central Building Research Institute (CBRI) has asked Edifice to provide the details about exact quantity of explosives that will be used for the implosion, following which the final clearance will be given, the officials said. The apex court has appointed CBRI as the monitoring authority for the demolition process.

The Edifice officials said that once procured, the explosives will be kept at an authorised warehouse permitted by the Petroleum and Explosive Safety Organisation in Palwal, Haryana, about 100km away from the site in Noida.

According to the officials, Edifice will conduct the demolition in collaboration with South African firm Jet Demolition that has expertise in similar cases. In 2019, Jet Demolition had razed the 108-metre-tall Bank of Lisbon building in Johannesburg that was situated within 7.8 metres of another building in a crowded area. The South African firm had used 920 kilos of explosives in 2,363 holes to demolish the building.

The twin towers in Noida are 103- metre-tall and the closest building — Aster 2 tower of Emerald Court — is eight metres away. Four 60-metre-tall high-rise apartment complexes in Maradu, Kerala, were demolished in January, 2021 for violation of coastal regulation zone norms.