Recently, several sophisticated constitutive models have been proposed to predict the behaviour of soils under cyclic loading. In this paper the concepts of the critical state soil mechanics have been used to develop a simple model which predicts many aspects of clays under repeated loading. The model employs the parameters that are usually associated with the Cam-clay family of models together with an additional parameter which characterises the cyclic behaviour. This parameter can conveniently be determined by performing cyclic triaxial tests under undrained conditions.
The behaviour of soils which are either, initially normally or initially overconsolidated is investigated for stress controlled and strain controlled loadings in the triaxial test. The results of this theoretical investigation show encouraging agreement with the results of laboratory tests on saturated clays, e.g. Taylor and Bacchus, 1969; Andersen, 1975, 1976.