Testing times at Scott Base

WSP Christchurch-based principal geotechnical engineer Mark Broughton travelled to Scott Base with Antarctica New Zealand and contractors from Leighs Construction and McMillan Civil for a three-week stint in November. Their aim - to see how quickly 500mm diameter pile holes could be drilled through permafrost, ice, basalt and scoria. They also assessed the performance of a technique to freeze the steel piles in place.

The piles will be a key part of the redevelopment of Scott Base. Look at the new base’s concept drawings and it quickly becomes clear why getting the piling right is so important. Three sleek interconnected buildings sit atop dozens of piles, which support the entire structure.

The team lowered a hollow circular steel test pile into a four-metre-deep pre-drilled hole. The pile had been fabricated to withstand ultra-low temperatures. Fresh water sourced from Scott Base’s reverse osmosis water plant was then poured down the hole to ice it in. Mark calls it "Antarctic cement".

The ground at Pram Point, Antarctica was more porous than expected and larger volumes of water were required. Different water sources, including colder sea water and mixing techniques were trialled to speed this process up.

Mark says WSP’s piling design accounts for seasonal thawing of permafrost and expected climate change impacts in the area.

“We know that the top 400mm of ground goes through the freeze thaw cycle. It’s important for us to make sure the piles get well below that. We’ve allowed additional pile depths based on global warming projections. At the end of the day, the piles are very robust. They’re sunk well and truly below the permafrost and into competent rock.”

Drilling one pile to four metres with the auger was slow going, but a down hole hammer tool was much faster, and Mark says once construction starts it would be realistic for the building contractor to place several piles a day.

With the new base having a five-decade lifespan, “the idea is that in 50 years' time we can come along, disconnect and remove the buildings, heat the inside of the piles, melt the ice and lift them out with an excavator,” he says.

Engineering in Antarctica comes with a unique set of environmental challenges. On this trip, while the outside temperature was a relatively mild -2° the wind chill at times dropped to a numbing minus 20°.

It was Mark's first trip to Antarctica and couldn't have been further removed from his geotechnical work in the more temperate landscapes of the South Island.

“It always took us a while to put our gear on. I was often fiddling around taking measurements, tightening bolts and taking photographs, which meant taking the gloves and goggles on and off. You get very cold from that. You’re always thinking about how you can get out of the wind too.”

Much of the science done at Scott Base focuses on how Antarctica and its ecosystems will be impacted by climate change and how those changes will influence the rest of the planet. Thanks to WSP’s geotechnical and civil engineering expertise, when the new base finally opens in 2028 it’s nice to know the research community will have a solid ‘foundation’ to work from.

More information about the redevelopment of Scott Base can be found here on the Antarctica New Zealand website.