Angle of Repose and Angle of Marginal Stability: Molecular Dynamics of Granular Particles

We present an implementation of realistic static friction in molecular dynamics (MD) simulations of granular particles. In our model, to break contacts between two particles, one has to apply a finite amount of force, determined by the Coulomb criterion. Using a two dimensional model, we show that piles generated by avalanches have a finite angle of repose θR (finite slopes). Furthermore, these piles are stable under tilting by an angle smaller than a non-zero tilting angle θT , showing that θR is different from the angle of marginal stability θMS , which is the maximum angle of stable piles. These measured angles are compared to a theoretical approximation. We also measure θMS by continuously adding particles on the top of a stable pile. PACS numbers: 46.10+z, 62.20-x Lee/Herrmann — July 21, 1992 PAGE 1