Sand is a fascinating material. It can flow and be poured like a liquid, but retains many of the properties of solids, clogging pipes or forming sand dunes. The behavior of collections of small particles like sand is known as granular physics, and is an immensely important field for the handling and transport of the wide range of granular materials out there like grains, rice, powders and the vast amounts of sand used in the construction industry.
source https://phys.org/news/2021-03-magic-sand-physics-granular.html
