Acoustic measurements of anisotropic elasticity in glass bead packings under uniaxial stress
Résumé
Coherent elastic waves are employed here to haracterize the anisotropic elasticity of the dry 3D granular assembly in the oedometer test. Bulk compressional (P-) and shear (S-) waves are measured when they propagate espectively along the vertical (load-) direction and horizontal one, being polarized in different direction. The obtained results illustrate clearly the elastic anisotropy of the contact network. The pressure-dependent velocity is analyzed within the effective medium approach based on the Hertz-Mindlin contact theory. The influence of the initial texture of granular media is also examined using different sample preparation procedures. Combined with the density and stress field measurements, our acoustic measurements suggest that the anisotropic elasticity of a glass bead packing induced in the oedometer test reflects the effect of the initial anisotropic texture.