Several models describing soil response under cyclic loading have been introduced in recent years with limited success. Most of these models are over-complex for realistic parameter identification.
In this study, a simple model for the behavior of clay under static and cyclic loading is developed. This model uses the hyperbolic representation for the stress-strain relationship and it describes undrained effective stress path based on the critical state theory. Proposed energy dissipation equation combines hyperbolic model with the critical state theory. The developed constitutive model can describe the behavior of clay in heavily overconsolidated state as well as lightly overconsolidated state under monotonic loading.
In order to extend the model for the behavior of clay under cyclic loading, equivalent overconsolidation concept and a shift function of path spacing ratio are introduced in the constitutive model developed for monotonic loading. Such two factors are applicable to any other constitutive models which are able to describe the overconsolidated behavior of clay. A single additional parameter is required to represent the cyclic effect and it can be reasonably determined. The measured behavior in undrained cyclic triaxial tests has been easily and precisely predicted by the newly developed constitutive model.
