Behavior of grains in contact with the wall of a silo during the initial instants of a discharge-driven collapse

• We study the collapse of thin walled cylindrical silos during granular discharges.
• We monitor the time-dependent behavior of grains in contact to the wall.
• Grains in contact with the wall start sliding after the collapse has been triggered.

We study experimentally gravity-driven granular discharges of laboratory scale silos, during the initial instants of the discharge. We investigate deformable wall silos around their critical collapse height, as well as rigid wall silos. We propose a criterion to determine a maximum time for the onset of the collapse and find that the onset of collapse always occurs before the grains adjacent to the wall are sliding down. We conclude that the evolution of the static friction towards a state of maximum mobilization plays a crucial role in the collapse of the silo.