Force distributions in three dimensional compressible granular packs
  We present an experimental investigation of the probability distribution of normal contact forces, $P(F)$, at the bottom boundary of static three dimensional packings of compressible granular materials. We find that the degree of deformation of individual grains plays a large role in determining the form of this distribution. For small amounts of deformation we find a small peak in $P(F)$ below the mean force with an exponential tail for forces larger than the mean force. As the degree of deformation is increased the peak at the mean force grows in height and the slope of the exponential tail increases. 
J. Michael Erikson, Nathan W. Mueggenburg, Heinrich M. Jaeger, and   Sidney R. Nagel