ABSTRACT
The stress-strain response of a geomaterial may change with the time chosen for the beginning of loading and changes in the loading rate. This phenomenon, depending on the type of geomaterial, moist conditions, dry density, temperature, stress and strain conditions, loading history and so on is called the time effects in general terms. To develop a relevant constitutive model that can simulate “the time effect” realistically under as possible as different conditions, it is necessary to properly define the time effect including “ageing effects” and “viscous or loading rate effects”. These two different aspects of the time effects should be linked to different basic mechanisms behind, such as “changes with time in the intrinsic material properties due to changes in interface and/or internal particle properties caused by a physico-chemical process” (ageing effects), “viscous sliding at inter-particle contact points” (viscous effects), “time dependent property of the particles”, among others.
