The study looked at how coal pillars in shallow mines can stay stable. They used computer simulations to see how the width of the pillars affects their strength. They found that the stress on the pillars mostly comes from above and below, causing them to fail by shearing. As the pillars get narrower, the stress inside them goes down until they reach a critical point where they could collapse. So, the width of the pillars is crucial for keeping them strong and safe.