Maximum angle of stability in wet and dry spherical granular media

We demonstrate that stability criteria can be used to calculate the maximum angle of stability ${\theta }_m$ of a granular medium composed of spherical particles in three dimensions and circular disks in two dimensions. The predicted angles are in good agreement with the experimental results. Furthermore, we determine the dependence of ${\theta }_m$ on cohesive forces, applying the results to wet granular material by calculating the dependence of ${\theta }_m$ on the liquid content of the material. We have also studied wet granular media experimentally and find good agreement between the theory and our experimental results.