What question did this study set out to answer?

This investigation aims to understand the conditions under which a sand heap becomes unstable when subjected to vertical vibrations.

January 2, 1989

Instability in a Sand Heap

Key Points

This investigation aims to understand the conditions under which a sand heap becomes unstable when subjected to vertical vibrations.
Utilized low-frequency vertical vibrations with a range of 10-1000 Hz.
Analyzed the free surface inclination angle and particle flow in the heap.
Identified vibration acceleration as a key control parameter.
The free surface of the sand heap becomes inclined at a specific angle due to vibrations.
A continuous flow of particles occurs down the inclined surface.
Convective transport refills the top of the heap with new beads.

Abstract

When a bead heap is submitted to low-frequency (2=10-1000 Hz) vertical vibrations at a large enough amplitude a, its horizontal free surface becomes unstable and a stationary state is reached. This one is characterized firstly by a free surface which is inclined within an angle to the horizontal, secondly by a continuous flow of particles rolling down the free surface, and thirdly by a convective transport inside the material which refills the top of the heap with new beads. We demonstrate that a control parameter is the vibration acceleration =a^2.

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Instability in a Sand Heap

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