Evidence of Raleigh-Hertz surface waves and shear stiffness anomaly in granular media

Abstract

Due to the non-linearity of Hertzian contacts, the speed of sound in granular matter increases with pressure. Under gravity, the non-linear elastic description predicts that acoustic propagation is only possible through surface modes, called Rayleigh-Hertz modes and guided by the index gradient. Here we directly evidence these modes in a controlled laboratory experiment and use them to probe the elastic properties of a granular packing under vanishing confining pressure. The shape and the dispersion relation of both transverse and sagittal modes are compared to the prediction of non-linear elasticity that includes finite size effects. This allows to test the existence of a shear stiffness anomaly close to the jamming transition.

4 pages 4 figures

References in corpus (4)

• Jamming at Zero Temperature and Zero Applied Stress: the Epitome of Disorder
• How Hertzian solitary waves interact with boundaries in a 1-D granular medium
• Excess Vibrational Modes and the Boson Peak in Model Glasses
• Force Mobilization and Generalized Isostaticity in Jammed Packings of Frictional Grains