Time-Dependent Behavior of Undisturbed Clay

Time dependence of undrained stress-strain and strength behavior of a natural sensitive marine clay has been investigated with particular reference to the effects of strain rate, strain rate history, aging, and thixotropy. Triaxial samples, identically consolidated, were sheared under a variety of time-loading histories in order to simulate various deformation rate histories. The stress-strain and strength results from these tests were correlated using the hypothesis that stress is a function of current strain and strain rate only. It is illustrated that a stiffer stress-strain response and an increase in undrained strength result from an increase in rate of strain, length of aging, and thixotropic hardening. However, the failure in terms of effective stresses is found to be independent of time effects of any kind whatsoever.