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Glass-like grains can constantly creep, research says


A study has found sand and soil in downhill formations can ‘creep’, despite a lack of disturbance, with an almost liquid-like nature. This has posed a raft of questions for those building, working or living near such materials and geographies.

Published in Nature Communications, the study was titled ‘The perpetual fragility of creeping hillslopes.’

Researchers used a laboratory hillslope where disturbances can be monitored and mitigated to observe how the granular material behaved.

“Surprisingly, we find that even an undisturbed sandpile creeps indefinitely, with rates and styles comparable to natural hillslopes,” the study stated.

“Our observations suggest a new model for soil as a creeping glass, wherein environmental disturbances maintain soil in a perpetually fragile state.”

The study found this comparison between grains and glasses to reveal “deep similarities” – in hindsight, a rather predictable finding as one can be made from the other.

One interesting finding related to the relaxation and strain of a hillslope.

In layman’s terms, an undisturbed hill remains loose and fragile until a disturbance comes along and causes strain between the soil particles, holding it in place.

“While vibrations in our experiments excited surficial flow, the underlying bulk became more rigid and less susceptible to future fluidisation. This finding may have relevance for landslide development from earthquakes and should be explored further,” the research stated.

“An improved model of soil creep is not only useful for predicting hillslope sediment transport; it will also help us to better understand how creeping soil accelerates to the yield point, which leads to catastrophic landslides.”

In the experiment, creep rates were found to be controllable based on the type of disturbance administered.

Heat was found to decelerate creep rates back to their original, constant value, while a more physical disturbance like tapping was found to accelerate creep rates.

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