Thèse de Doctorat de l’Université Pierre et Marie Curie Spécialité: Physique École doctorale 107: Physique de la Région Parisienne

At large packing fraction, disordered packings of particles with repulsive contact interactions jam into a rigid state where they withstand finite shear stresses before yielding. For frictionless particles at zero temperature, the Jamming transition coincides with the onset of iso-staticity. Various geometrical and mechanical properties exhibit critical behavior with the distance to Jamming. What vestiges of Jamming remain at finite temperature and how Jamming impacts the thermodynamics of glasses remain open issues. We address these questions experimentally by investigating the dynamics of both the density field and the force network of an horizontally shaken bi-disperse packing of photo-elastic disks while varying the packing fraction, φ, at several vibration amplitudes γ. Although disks displacements reveal a slow global convective dynamics, strongly collective and intermittent motions take place on length scale much smaller than the grain diameter. These so-called dynamical heterogeneities are maximum at an intermediate packing fraction φ(γ). The statics and dynamics of the contact network display, respectively, two distinct sharp signatures, which are reminiscent of the glass transition phenomenology, albeit occurring at the contact scale. A dynamical signature occurs at φ(γ), and we relate it to the dynamical heterogeneities of the displacements. The static signature occurs at a larger packing fraction φJ(γ). We show further that φ(γ) and φJ(γ) merge in the γ → 0 limit and that the dynamical signature strongly increases as the vibration amplitude is reduced. These results are discussed in light of thermal soft-sphere properties close to Jamming. te l-0 07 64 09 3, v er si on 2 14 J an 2 01 3