Time dependent mechanical behaviour of loose sands

The time dependency of loose sands mechanical behaviour has been experimentally analysed and theoretically interpreted. A series of load controlled triaxial tests, by imposing finite load increments, has been performed. The single load increments are followed by variable time periods, in order to carry out many classical creep tests. According to the authors, the considered time dependency is due to the internal fabric rearrangement of the granular assembly, i.e. to the plastic strain development with time. This mechanical peculiarity is theoretically interpreted by means of an elastoviscoplastic constitutive model. This is a very simple extension of a previous incremental elastoplastic constitutive model and appears to be capable to reproduce experimental data quite well. Finally, the importance of the considered time dependency is underlined, both by considering numerical solutions and in analysing unstable natural and experimental phenomena.