ABSTRACT
Time dependent behavior of granularmaterials is quite different from the viscous behavior observed in clays. The effects of strain-rate, creep and stress relaxation of clays follow a classic pattern of viscous behavior observed for most materials. For such materials the stiffness and strength increase with increasing strain rate and phenomena such as creep, relaxation and strain rate effects are governedby the samebasicmechanism. This behavior is denoted as ‘‘isotach’’ behavior, i.e. there is a unique stress-strain-strain rate relation for a given clay. For such materials, the creep properties may be obtained from, say, a triaxial compression test and used for prediction of stress relaxation in another experiment.
