Stresses in silos: Comparison between theoretical models and new experiments

We present precise and reproducible mean pressure measurements at the botto m of a cylindrical granular column. if a constant overload is added, the pr essure is linear in overload and nonmonotonic in the column height. The res ults are quantitatively consistent with a local, linear relation between st ress components, as was recently proposed by some of us. They contradict th e simplest classical (Janssen) approximation, and may rather severely test competing models.