Studying the Stability of Piled Spheres: Understanding the Collapse Points of Granular Arrangements


A team of physicists and mechanical engineers from Chilean universities has made a significant discovery in understanding the stability of granularly arranged monolayers in a single pile with tilted slopes. Led by researchers from Universidad de Antofagasta, Universidad Autónoma de Chile, and Universidad de O’Higgins, the team developed computer simulations to model piled spheres, such as oranges, stacked with various slopes to determine the tipping point at which the pile collapses when one or more spheres are removed from the edge. The findings, published in the journal Physical Review E, shed light on the potential collapse scenarios of piled fruits in grocery stores, offering valuable insights for optimizing fruit displays and preventing accidents.

Many grocery stores showcase their fruits by creating aesthetically pleasing and inviting piles. These heaps typically feature sloped edges, which can give the impression of instability. Despite their appeal, these arrangements carry the risk of collapse if an unwary shopper accidentally removes a single fruit from an unstable section of the pile. The research team aimed to identify the precise tipping points of such piles to better understand the forces at play and the potential for collapse.

To achieve this, the researchers conducted computer simulations that accurately depicted stacked spherical objects of varying sizes and edge slopes. They explored a range of configurations, from mild slopes to extreme angles, to determine the conditions under which the pile collapses when one or more spheres are removed from the sloped edge. The simulations revealed that piles with extreme slopes can collapse with the removal of just one sphere. On the other hand, piles with modest slopes showed greater resilience, allowing for the removal of numerous spheres without experiencing collapse. However, predicting collapse scenarios became more challenging when slopes were in between the extremes.

By gradually increasing the slope angle, the researchers identified situations where the removal of multiple spheres, rather than just one, could trigger collapse. In addition, they calculated that under typical circumstances found in a grocery store setting, around 10% of the spheres (e.g., apples, oranges, or grapefruit) needed to be removed before the pile collapses. Therefore, a single shopper removing a single piece of fruit is unlikely to induce a collapse, unless several previous shoppers have done the same from the same location.

Building on these findings, the research team intends to expand their investigations to explore possible collapse scenarios in other real-world contexts. For example, they plan to examine piles of rocks with varying sizes. By better understanding the stability of different types of granular arrangements, their work aims to enhance safety measures and prevent accidents in environments where piled objects are common.

The team’s research offers valuable insights into the dynamics of stacked objects and provides a scientific basis for optimizing the displays of piled fruits and other commodities. By implementing the knowledge gained from these simulations, grocery stores and other retailers can improve the stability of their product presentations, minimizing the risk of collapse and ensuring a safer shopping experience for customers.

1. Source: Coherent Market Insights, Public sources, Desk research
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