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 contact 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 theta(R) (finite slopes). Furthermore, these piles are stable under tilting by an angle smaller than a non-zero tilting angle theta(T), showing that theta(R) is different from the angle of marginal stability theta(MS), which is the maximum angle of stable piles. These measured angles are compared to a theoretical approximation. We also measure theta(MS) by continuously adding particles on the top of a stable pile.