Searching the sand for answers on impact of Canterbury earthquakes video

IAIN MCGREGOR

Liquefaction spewed out of the ground outside Danny Morris' property on Broadhaven Ave, Parklands, after the earthquake.

A Canterbury scientist did not expect to get fresh samples for his study on the effects of liquefaction. 

Lincoln University associate professor Peter Almond spent a fortnight studying a vacant site at Kairaki Beach earlier this month, looking at the effects of liquefaction beneath the surface.

He did not expect when he left on February 12 that he would be back again three days later to analyse fresh samples.

Lincoln University associate professor, Peter Almond, surveying liquefaction at Kairaki Beach.
JONATHAN LEASK/FAIRFAX NZ

Lincoln University associate professor, Peter Almond, surveying liquefaction at Kairaki Beach.

The magnitude 5.7 earthquake in Christchurch on Valentines Day gave him "fresh evidence" and added a "new dimension" to his study. 

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Kairaki Beach had a high water table and sandy sediment make-up due to its proximity to the Waimakariri River and the ocean, making it prone to liquefaction – and an ideal study site. 

"It is a site that liquefied in September 2010 and again in February 2011, as well as other subsequent quakes, and we have aerial photographs to show us that," Almond said.

"We are using the site to help us calibrate, when we find evidence of past liquefaction in soil profiles elsewhere."

Almond identified "sand blows", from aerial photographs – volcano-like deposits left on the surface from liquefaction – and dug trenches in those locations.

"We want to see what distinctive signatures in the soil profile liquefaction leaves behind," he said.

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Almond's research would be used by council and hazard management groups to identify areas needing higher levels of geotechnical investigation before being built on,.

The results could also help determine the level of ground stabilisation required for construction.

"In some of the trenches, we have found features which are really enigmatic. We can't understand quite how they formed by liquefaction," he said.

 - Stuff

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