  This paper, in French, describes a series of completely different behaviours
of the mechanics of granular matter, which are obtained experimentally using
periodic forcing at different amplitude, frequency and orientation. It starts
with the problem of granular dissipative gas which has been investigated in
micro-gravity ; it is found that such a gas exists only at very low density ;
it is shown also that clustering occurs at larger density. Is this a phase
transition ? The problem of dissipative Sinai billiard is then investigated
briefly ; is it ergodic ? An experiment on propagation of acoustic wave is
studied, with peculiar attention paid to scattering and diffusion that occurs
when acoustic wavelength is comparable to the grain size. A third experiment
demonstrates that bulk convection can be induced by slow (quasi static)
horizontal forcing ; this flow is related to the quasi static rheology of
granular matter, but looks rather like convection occurring under "dynamic
vibration". A fourth experiment describes pure inertial effect, making the sand
behaving as a perfect (non viscous) fluid ; in particular, it is shown that a
static swell 9that does not propagate) is enforced at the interface between
liquid and sand by strong periodic horizontal forcing . Pacs # : 5.40 ; 45.70 ;
62.20 ; 83.70.Fn
