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3-D imaging reveals the inner workings of avalanches, earthquakes

By Brooks Hays

DURHAM, N.C., March 5 (UPI) -- What triggers an avalanche? What enables a landslide? Why don't we sink into the sand when walking on the beach? What happens to the soil during the rumbling of an earthquake?

These are all questions scientists at Duke University have been working to answer using 3-D imaging that allows them to peer inside the mechanical dynamics of high-pressure situations involving granular substances -- like snow, soil and sand.

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A complex amalgamation of force sensors, digital cameras and advanced computer algorithms have allowed researchers to penetrate these substances and pinpoint the forces exerted by neighboring particles in three dimensions.

Instead of using actual sand, snow or soil, scientists stacked hundreds of translucent hydrogel beads in a Plexiglass box to simulate the density and physical characteristics of each substance. As pistons repeatedly pushed down on the beads, cameras and sensors captured cross-sectional snapshots.

Researchers were able to detail the tiny indentations as pressurization pushed the particles together -- revealing the forces exerted on each other.

The researchers are now using the newly gleaned data to better model the mechanical behaviors of granular substances during larger-scale geologic phenomena.

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"This gives us hope of understanding what happens in disasters like a landslide, when packed soil and rocks on a mountain become loose and slide down," study co-author Nicolas Brodu, now a researcher at the French Institute for Research in Computer Science and Automation, said in a press release.

"First it acts like a solid, and then for reasons physicists don't completely understand, all of a sudden it destabilizes and starts to flow like a liquid," Brodu added. "This transition from solid to liquid can only be understood if you know what's going on inside the soil."

The new study was published this week in the journal Nature Communications.

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