  We present a new model for relaxations in piles of granular material. The
relaxations are determined by a stochastic rule which models the effect of
friction between the grains. We find power-law distributions for avalanche
sizes and lifetimes characterized by the exponents $\tau = 1.53 \pm 0.05$ and
$y = 1.84 \pm 0.05$, respectively. For the discharge events, we find a
characteristic size that scales with the system size as $L^\mu$, with $\mu =
1.20 \pm 0.05$. We also find that the frequency of the discharge events
decrease with the system size as $L^{-\mu'}$ with $\mu' = 1.20 \pm 0.05$.
