Transient dynamics of a 2D granular pile

We investigate by means of Contact Dynamics simulations the transient dynamics of a 2D granular pile set into motion by applying shear velocity during a short time interval to all particles. The spreading dynamics is directly controlled by the input energy whereas in recent studies of column collapse the dynamics scales with the initial potential energy of the column. As in column collapse, we observe a power-law dependence of the runout distance with respect to the input energy with nontrivial exponents. This suggests that the power-law behavior is a generic feature of granular dynamics, and the values of the exponents reflect the distribution of kinetic energy inside the material. We observe two regimes with different values of the exponents: the low-energy regime reflects the destabilization of the pile by the impact with a runout time independent of the input energy whereas the high-energy regime is governed by the input energy. We show that the evolution of the pile in the high-energy regime can be described by a characteristic decay time and the available energy after the pile is destabilized.

Reference:

• Mutabaruka, P., Kumar, K., Soga, K., Radjai, F. and Delenne, J.Y., 2015. Transient dynamics of a 2D granular pile. The European Physical Journal E, 38(5), p.47. article

The same velocity applied to all particles

The same velocity applied to a column of particles adjacent to the left wall

A constant velocity gradient is applied

Note that the first two pushing modes mimic the case of a pile impacted from the left by a moving mass (tsunami, debris…) whereas the last mode represents energy transfer by horizontal quake of the bottom line.