We present measurements of the vertical stress profile $\sigma$ on the base of flat-bottomed cylindrical silos discharged through an orifice centered on its base. An overweight forces the material on top of the free surface. The mean bottom pressure $\sigma (z,D,W)$, with $z$ the height of the granular column, $D$ the silo diameter, and $W$ the mass of the overweight, increases significantly at the end of the discharge. Inspired by early models of stress distribution, we show that $\sigma$ measured at $z=0$ can be rescaled to yield a collapse of the data, as a function of $z/D$, for all $D$ and $W$ explored. We also show that the profile $\sigma \left(r\right)$ is self-similar as a function of the radial coordinate $r$ and can be rescaled to collapse the data for different $z,D$, and $W$. Although the model correctly predicts the functional dependences, it fails in quantitative terms. These results challenge our understanding of free and forced granular flows through orifices.

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• Granular flows
• Dry granular materials
• Granular fluids
• Granular materials