  We compare the structural and mechanical properties of mechanically stable
(MS) packings of frictional disks in two spatial dimensions (2D) generated with
isotropic compression and simple shear protocols from discrete element modeling
(DEM) simulations. We find that the average contact number and packing fraction
at jamming onset are similar (with relative deviations $< 0.5\%$) for MS
packings generated via compression and shear. In contrast, the average stress
anisotropy $\langle {\hat \Sigma}_{xy} \rangle = 0$ for MS packings generated
via isotropic compression, whereas $\langle {\hat \Sigma}_{xy} \rangle >0$ for
MS packings generated via simple shear. To investigate the difference in the
stress state of MS packings, we develop packing-generation protocols to first
unjam the MS packings, remove the frictional contacts, and then rejam them.
Using these protocols, we are able to obtain rejammed packings with nearly
identical particle positions and stress anisotropy distributions compared to
the original jammed packings. However, we find that when we directly compare
the original jammed packings and rejammed ones, there are finite stress
anisotropy deviations $\Delta {\hat \Sigma}_{xy}$. The deviations are smaller
than the stress anisotropy fluctuations obtained by enumerating the force
solutions within the null space of the contact networks generated via the DEM
simulations. These results emphasize that even though the compression and shear
jamming protocols generate packings with the same contact networks, there can
be residual differences in the normal and tangential forces at each contact,
and thus differences in the stress anisotropy.
