  We study numerical simulations of large (N~10^4) two-dimensional quasi-static
granular assemblies subjected to a slowly increasing deviator stress. We report
some peculiarities in the behavior of these packings that have not yet been
adressed. The number of sliding contacts is not necessarily related to
stability: first the number of sliding contacts rises linearly and smoothly
with the applied stress. Then, at approximately half the peak stress, the
increase slows down, a plateau develops, and a decrease follows.
