A generalized model for clay under monotonic and cyclic loading conditions

In this paper a kinematic hardening model for clay has been proposed to replace a previously proposed kinematic hardening model which could not predict the observed stabilization characteristics of strains and change of stress-dilatancy relation of clay during cyclic loading. Also, the present model can account for both positive and negative dilatancy as well as the increase of strength (friction angle) due to over consolidation or cyclic loading. All these features have been achieved by modifying hardening function and plastic potential function taking over consolidation ratio as the controlling factor. This model is equally applicable to the normally consolidated clay and closely predicts the strength and dilatancy characteristics. Apart from the conventional clay models (e.g. Cam clay model), this model uses a modified stress tensor (t(ij)), which has made it possible to consider the effect of intermediate principal stress on the strength and dilatancy characteristics. It has been assumed that the plastic strain increment vector is composed of two components, one satisfies associated flow rule in t(ij)-space and the other is linked with the increase of normal stress. Finally, the new kinematic clay model has been verified by experimental results.