Abstract:

Using a developed low frequency inverted torsion pendulum, the relative energy dissipation in sheared granular materials is investigated. The amplitude and the frequency spectra of fine sand and glass beads are measured. The results show that with the increase of amplitude, one peak of energy dissipation is found in amplitude spectra; while with increasing frequency, four peaks of energy dissipation are observed in the curves of frequency spectra, corresponding to four decreases of the relative modulus. And there exists a peak (corresponding to a critical depth) in the curves of relative energy dissipation along with the inserted depth of probe with different oscillating amplitudes. Based on the mesoscopical analysis of granular materials, a rheological model is presented to explain the rheological dissipation mechanics; and the results indicate that the friction among particles not only dissipates the energy but also enhances the elasticity of the system. The frequency spectra of fine sand reveal a different dissipation: the resonant dissipation.

Key words: granular material, energy dissipation, force chain