Amandine Miksic, ISC-CNR Roma #
Evolution of the grain contacts in a granular sample under creep and 
stress-relaxation #
This work deals with the characterization, using an acoustic technique, of 
the mechanical behavior of a dry dense granular medium under quasi-static 
loading. The ultrasound propagation through the contact-force network 
supporting the external load offers a non-invasive probe of the 
viscoelastic properties of such heterogeneous media. First, the response 
of the glass bead packing is studied during creep and relaxation tests 
under oedometric configuration. A quasi-logarithmic increase of sound 
velocities is found in both mechanical tests. A model based on the 
mechanics of micro-contact between rough grains describes fairly well our 
experimental results, especially for the evolution of elastic modulus. 
Another main experimental finding is that collective grains rearrangements 
within the packing also play a crucial role at the early stage of creep 
and relaxation