  We report recent results of molecular dynamics simulations of frictional
athermal particles at constant volume fraction and constant applied shear
stress, focusing on a range of control parameters where the system first flows,
but then jams after a time tjam. On decreasing the volume fraction, the mean
jamming time diverges, while its sample fluctuations become so large that the
jamming time probability distribution P(tjam) becomes a power-law. We obtain an
insight on the origin of this phenomenology focusing on the flowing regime,
which is characterized by the presence of a clear correlation between the shear
velocity and the mean number of contacts per particles Z, whereby small
velocities occur when Z acquires higher values.
