  We study experimentally the relaxation towards mechanical equilibrium of a
granular pile which has just experienced an avalanche and discuss it in the
more general context of the granular jamming transition. Two coexisting
dynamics are observed in the surface layer: a short time exponential decay
consisting in rapid and independent moves of grains and intermittent bursts
consisting in spatially correlated moves lasting for longer time. The
competition of both dynamics results in long-lived intermittent transients, the
total duration of which can late more than a thousand of seconds. We measure a
two-time relaxation function, and relate it via a simple statistical model to a
more usual two-time correlation function which exhibits strong similarities
with auto-correlation functions found in aging systems. Localized perturbation
experiments also allow us to test the pile surface layer receptivity.

Soft Condensed Matter;Disordered Systems and Neural Networks