Still on the topic of sand, but more related to its dynamics than its softness, I would like to recommend the work of Per Bak [1]. Among other things he invest

Still on the topic of sand, but more related to its dynamics than its softness, I would like to recommend the work of Per Bak [1]. Among other things he investigated and modeled the frequency and magnitude of avalanches in piles of sand, work that lead to the concept of self-organized criticality [2]. [1] https://en.wikipedia.org/wiki/Per_Bak https://en.wikipedia.org/wiki/Per_Bak [2] https://en.wikipedia.org/wiki/Self-organized_criticality https://en.wikipedia.org/wiki/Self-organized_criticality