What does the angle of repose depend on?

The angle of repose is the maximum angle at which a pile of a granular material, like sand or gravel, can remain stable without sliding. This angle is primarily influenced by the forces acting on the particles composing the material. Gravity plays a key role, as it pulls the particles downward, while friction determines how well those particles can resist sliding against one another.

When particles are stacked at an angle greater than the angle of repose, gravity's force overcomes the friction holding the particles together, causing them to slide. Thus, both gravity, which impacts how strongly the particles are pulled down the slope, and friction, which helps them stay in place, are essential factors that dictate the angle of repose. The relationship between these two forces establishes the balance required for stability at a particular inclination.