  The measurement of force distributions in sandpiles provides a useful way to
test concepts and models of the way forces propagate within noncohesive
granular materials. Recent theory by Bouchaud et al. implies that the internal
structure of a heap (and therefore the force pathway) is a strong function of
the construction history. In general, it is difficult to obtain information
that could test this idea from 3D granular experiments except at boundaries.
However, 2D systems, such as those used here, can yield information on forces
and particle arrangements in the interior of a sample. We obtain position and
force information through the use of photoelastic particles. These experiments
show that the history of the heap formation has a dramatic effect on the
arrangement of particles (texture) and a weaker but clear effect on the forces
within the sample. Specifically, heaps prepared by pouring from a point source
show strong anisotropy in the contact angle distribution. Depending on
additional details, they show a stress dip near the center. Heaps formed from a
broad source show relatively little contact angle anisotropy and no indication
of a stress dip.
