Aging in granular columns

Abstract

This work presents a study of the temporal evolution of granular matter confined in narrow columns. Grains are added into the containers and let them evolve for 6 to 10 hours. Two temporal regions are identified: an initial relaxation independent of volume with an average relaxation time of τ ≈ 900 s; and long-term regime where the system saturates and shows fluctuations around this saturation mass. These fluctuations are characterised by distributions with a fourth moment which slightly differs from the one of a Gaussian distribution. Both responses have been analysed for different added masses that correspond to different mechanical properties of the granular pile. Finally, it is observed that different experiments under the same conditions end up in different final states characterised by different apparent masses. In the saturation regime, the relative fluctuations of apparent mass between configurations show a power-law decay as a function of the total number of grains N−0.61.