Silo collapse under granular discharge

TL;DR

This study explores how cylindrical shells collapse under granular discharge, revealing stabilization effects due to granular wall friction and grain size influence, supported by a new fluid/structure theory and experimental validation.

Contribution

It introduces a novel fluid/structure theory that accounts for granular friction and imperfections, providing new scaling laws for silo collapse under granular discharge.

Findings

Critical filling height exceeds standard buckling estimates.

Granular wall friction stabilizes shells below collapse threshold.

Grain size significantly affects collapse behavior.

Abstract

We investigate, at a laboratory scale, the collapse of cylindrical shells of radius $R$ and thickness $t$ induced by a granular discharge. We measure the critical filling height for which the structure fails upon discharge. We observe that the silos sustain filling heights significantly above an estimation obtained by coupling standard shell-buckling and granular stress distribution theories. Two effects contribute to stabilize the structure: (i) below the critical filling height, a dynamical stabilization due to granular wall friction prevents the localized shell-buckling modes to grow irreversibly; (ii) above the critical filling height, collapse occurs before the downward sliding motion of the whole granular column sets in, such that only a partial friction mobilization is at play. However, we notice also that the critical filling height is reduced as the grain size, $d$, increases. The importance of grain size contribution is controlled by the ratio $d/\sqrt{R t}$. We rationalize these antagonist effects with a novel fluid/structure theory both accounting for the actual status of granular friction at the wall and the inherent shell imperfections mediated by the grains. This theory yields new scaling predictions which are compared with the experimental results.