Stick-slip Transition in the Scalar Arching Model
  When some granular material contained into a silo is pushed upwards with a piston, an irregular stick-slip motion of the system of grains is observed. We show how one can adapt the `Scalar Arching Model' -- proposed as a model for giant stress fluctuations in silos -- in order to describe this stick-slip phenomenon. As a function of the sensitivity of the system to mechanical noise, the system exhibit two different phases: a `jammed' phase, and a `sliding' phase where irregular stick-slip is observed. We analyze the transition, which is found to be of mean-field type, and study the statistical properties of the intermittent stick-slip motion. 
Philippe Claudin and Jean-Philippe Bouchaud