The role of Rayleigh Waves in Granular Solids

Wave propagation in granular solids is found to have at least two regimes: a low-frequency ballistic signal and a high-frequency diffusive tail. The latter is attributed to granules clapping or elastic waves within the granules themselves. The low frequency front is traditionally attributed to the rigid-body motion of particles and their interactions via quasi-static contact forces. We present results obtained with experimental and numerical models indicating that the low-frequency ballistic wavefront is itself the result of surface waves in the granules. We find surface waves to be the principal mechanism of energy transmission.