Vibrations from the demolition of the twin towers are unlikely to cause any structural damage to nearby buildings, a study by a UK-based firm has said.
Vibrock, which was hired by Jet Demolitions to carry out the study, said the vibrations might cause “some very minor cosmetic damage” — like cracks in “fine plaster”. South Africa’s Jet Demolitions is the partner of Edifice Engineering, which is supposed to carry out the demolitions, and has prepared the blast design.
Officials said the Vibrock report was on Monday shared with the Noida Authority, the developer Supertech and CBRI. The twin towers — Apex and Ceyane — are set to be demolished on August 21.
The study covered the possible air overpressure and ground-borne vibration at the time the two towers will be brought down. It took into account the blast design, the weight and height of the two towers and Vibrock’s in-house database of similar projects in the past.
According to the report, the closest residential receptor is the 12-storey tower of Aster 2, which is just 9 metres from Apex. There is also a gas pipeline, which is 3-4 metres under the ground and just 16 metres from the two towers.
“The predicted ground vibration levels range from 22 mms (millimetre per second) to 34 mms at a separation distance of 10 metres to a most likely 3 mms to 5 mms at a separation distance of 100 metres. At the apartment block (Aster 2), a most likely 25 mms, to a maximum likely 36 mms is predicted. From the British Standard, levels of vibration for the prevention of hairline plaster cracking range from 15 mms to 50 mms depending upon vibration frequency. Where such worst case values exceed 15 mms there is some slight risk of some very minor cosmetic damage, i.e. the very finest of plaster cracking. The predicted vibration levels are however below the levels which would cause structural damage to the building,” the report stated.
On the ground surface, vibrations in the range of 18-27 mms are predicted, which are also considered safe. As a precautionary measure for the gas pipeline below, steel plates of 10-12 mm will be laid on the ground. Trenches will also be dug on the ground surrounding the pipeline.
“The report reiterates what we have been saying from the beginning. No structural damage will happen to the nearby buildings. The buildings constructed here are made to withstand earthquakes of 4-5 on the Richter scale,” said Uttkarsh Mehta, a partner in Edifice.
