ABSTRACT
The response of soils to cyclic loading may be modelled to various levels of sophistication, depending on the task in hand. Models based on complete stress-strain histories may be too complex for use in practice and too sophisticated for fast development, but are expected to provide a sound basis for simpler, practical models in the long term. The concept of a stress-reversal surface may be introduced most simply by using a yield surface as an example. Stress-reversal in this case occurs when a stress point initially moving in contact with the yield surface moves away from it, the constitutive law changing from plastic to elastic. During the early stages of unloading, however, any surface just contacted by the stress point passes through the stress-reversal point, so that its radius is equal to half the distance between the stress point and the stress-reversal point.
