  The force network of a granular assembly, defined by the contact network and
the corresponding contact forces, carries valuable information about the state
of the packing. Simple analysis of these networks based on the distribution of
force strengths is rather insensitive to the changes in preparation protocols
or to the types of particles. In this paper we consider two dimensional
simulations of tapped systems built from frictional disks and pentagons, and
study the structure of the force networks of granular packings by considering
network's topology as force thresholds are varied. We show that the number of
clusters and loops observed in the force networks as a function of the force
threshold are markedly different for disks and pentagons if the tangential
contact forces are considered, whereas they are surprisingly similar for the
network defined by the normal forces. In particular, the results indicate that,
overall, the force network is more heterogeneous for disks than for pentagons.
Additionally, we show that the states obtained by tapping with different
intensities that display similar packing fraction are difficult to distinguish
based on simple topological invariants.
