Viscoplastic modeling of granular column collapse with pressure-dependent rheology

Using an easily calculated order of magnitude approximation of the mean viscosity during the flow (η=1 Pa s here), we show that a Drucker-Prager rheology with a constant viscosity gives results very similar to the μ(I) rheology and agrees with experimental height profiles, while significantly reducing the computational cost. Within the range of viscosities 0.1<η<1 Pa s, the dynamics and deposits are very similar. The observed slumping behavior therefore appears to be mainly due to the flow/no-flow criterion and to the associated strain-independent part of the “flowing constitutive relation” (i.e. related to plastic effects). However, the results are very different when an unrealistically large value of viscosity (10 Pa s) is used.