Wreckers Dismantling close off 2018 with a bang in South AfricaPublished 27/12, 2018 at 10:33
Despite depressed business conditions in the South African demolition industry, local company Wreckers Dismantling has successfully ended the year with two challenging explosive demolitions in difficult locations.
This included in October, a controlled explosives operation downing a 45m headgear at Shaft 5 of Harmony Gold Mine at Secunda in Mpumalanga province.
Explosives specialist for Wreckers Dismantling, Kyle Perkin, says the project was ‘challenging’, with the structure being supported by compound girders. Once the explosives were detonated there was a possibility that shrapnel could travel as far as 1k if not properly controlled. “Special cutting techniques were adopted for the placing of the charges as well. These had to be very precise, so as not to overly pre weaken the structure, causing premature collapse,” explains Perkin.
Indirectly linked to the gold mining industry, was the mid November removal of the first two of four original floodlight towers at the Willowmore Park international cricket ground in Benoni, on the East Rand in Gauteng province. The five second demolition of the 70 year old towers took place once the relevant heritage authorities had approved their removal, in keeping with South African law regarding structures older than 60 years. Perkin explains the demolition: “The ground’s lights have steel pylons, and there were concerns that the natural structural deterioration of the disused concrete towers over the years had made them potentially unable to withstand a significant earth tremor. This capacity must be factored into any construction in the area, due to extensive mining activity on the East Rand over more than a century.”
There were many other factors to consider; from protection at source of the blast to public safety, damages to underlying services, road closures and an exclusion zone of 200m. Given the proximity of an electric substation, and ablution blocks just 4m away from each mast, it was crucial that both towers were felled in the desired direction to prevent damages. “So we removed a large portion of the circumference of the tower with controlled explosives, and left the remainder to act as a hinge as the towers started to rotate past the centre of gravity,” says Perkin.
Both towers demolition was initiated simultaneously as air blast was not a concern. Soil was placed to cushion underlying cables from any major impact. Once both towers were successfully downed, processing and clearance commenced immediately to meet pressing sports needs at the ground in the middle of the sport season. The remaining two towers, in more difficult locations at the ground, will be felled in April 2019.