World Demolition Summit 2016: High-risk demolition reaches new heights

Earthquakes, aftershocks and landslides make the already dangerous demolition industry even more risky. During the seventh annual Word Demolition Summit, Oct. 14, at the Marriott Biscayne Bay in Miami, Dr. Jan Kupec, technical director, ground engineering/infrastructure for New Zealand-based Aurecon Group, shared how a group of houses on an unstable cliff edge are being carefully demolished in the aftermath of major earthquakes in Christchurch, New Zealand.

During the event, organized by U.K.-based KHL Group, publisher of Demolition & Recycling International, in cooperation with the National Demolition Association (NDA), Washington, Kupec said two earthquakes which hit the area in created some 12,000 aftershocks.

Hagley Park was a housing development particularly hard hit. It affected 70 percent of the living area. The government offered by to buy the properties and take care of the demolition. It created the Canterbury Earthquake Recovery Authority (CERA).

Areas known as Deans Head and Shag Rock Reserve where many houses were located lost 75 meters of cliff edge during the first earthquake and about half of that during the second earthquake. Because of seismic shaking, Kupec said both events resulted in houses hanging over the cliff edge. His firm was responsible for demolishing 800 structures amidst 15 ton boulders that could move at any minute “and there were about 15,000 of them,” said Kupec.

He said the procurement process was complicated and that price was not the driver. He said he knew the demolition team would not be able to take the buildings down in a conventional way. Extensive landslides and several hundred retaining walls were just some of the risks. The government also wanted to protect the road below the cliff.

“They [CERA] told us find the safest way to do demolitions without harming anybody,” said Kupec.

“We couldn’t get to [the structures] any conventional way,” he said.

Kupec explained how the crews were “reducing the impact and making things safer by going through a very detailed engineering process to ensure what we do on the site is the safest possible solution we can come up with.”

Remote control demolition has been part of the process. Protranz was hired to do the work with a remote-controlled excavator. In order to accurately predict what the site conditions are, demolition crews have employed digital laser scanners and drones to take photos. The images are put into a program that graphs the photos.

They also used Google Earth, and Google Streetview to take a spherical photos and are employing mixed reality Kupec said, “Before going into potentially unsafe site, [we] can overlay useful information and break it manually down into manageable chunks, so people can use it.”

“A 3-D model gives us model of the side [and we] generate cross sections and determine rockfall analysis,” he explained.

He said crews were using technology to provide information in a meaningful manner and “in a relatively innovative way.”

The project is about 80 percent finished and Kupec says, “The site has changing conditions daily. Aftershocks are part of what can still happen on a site for us.”

The World Demolition Summit was Oct. 14 in Miami.