  Heterogeneity is classified in five categories---topologic, geometric,
kinematic, static, and constitutive---and the first four categories are
investigated in a numerical DEM simulation of biaxial compression. The
simulation experiments show that the topology and geometric fabric become more
variable during loading. The measured fluctuations in inter-particle movements
are large, they increase with loading, and they extend to distances of at least
eight particle diameters. Deformation and rotation heterogeneity are large and
are expressed in spatial patterning. Stress heterogeneity is moderate
throughout loading.
