  In this letter, we focus on the size effect of granular column collapses,
which are potentially connected to the dynamics of complex geophysical flows,
even if the link between microscopic structures of granular assemblies and
their macroscopic behaviors is still not well understood. Using the
sphero-polyhedral discrete element method (DEM), we show that the column
radius/grain size ratio has a strong influence on the collapse behavior. A
finite-size analysis, which is inspired by a phase transition around an
inflection point, is performed to obtain a general scaling equation with
critical exponents for run-out distances. We further link the size effect with
the strong force network and formalize a correlation length scale that
exponentially scales with the effective aspect ratio. Such a scaling solution
shows similarities with the percolation problem of two-dimensional random
networks and can be extended to other similar natural and engineering systems.
