We report experiments on the vibration-induced unclogging process in a silo. Arches blocking the orifice are perturbed by a gentle vibration intensity (below the fluidization limit). We explore how the endurance and the morphology of arches are affected by the applied perturbation. By performing a survival analysis of the breaking times we characterize the stability of arches. We use two geometrical variables to describe the arch morphology at two instants: when vibration starts and right before the collapse. Regardless of the morphological descriptor, it is confirmed that the arches that are initially more irregular are more unstable, but even so, it should not be taken for granted that the initial configuration unequivocally determines the endurance of any particular clog. Furthermore, the final configurations reveal that there exists a maximum degree of irregularity that the arches can withstand (before the collapse occurs), which is independent of the shaking strength.
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