A constitutive model for structured clays

A simple constitutive model for structured clays is presented. The model is based on an existing constitutive model for reconstituted clays. It uses a fixed relationship between change in sensitivity and plastic strain to represent destructuration so that all predicted effects of structure are included in the value of sensitivity. Only three added parameters are required, which can each be derived from a single isotropic compression test. All other parameters are the same as those used in the base model, which are derived from test data on reconstituted specimens. A value of ultimate sensitivity greater than unity allows the model to simulate clays with stable and/or metastable structure. Results from a parametric study show that the model predicts responses during compression and shearing typical of natural clays. The model was applied to test data from a natural soft clay using parameters derived where possible from isotropic compression tests. Results from the analyses prove that the simplified formulation of the model is sufficient to significantly improve predictions.