ABSTRACT
Constitutive modelling is at the heart of modern soil mechanics because it enables numerical simulations of various boundary value problems when they are implemented in finite element or finite difference programs. This is essential not only for carrying out parametric studies to understand what is key to the engineering behaviour of soils but also as an aid to engineering design. Here a relatively simple state-dependent elasto-plastic model for both
saturated and unsaturated soils is developed. The model, which is formulated under the critical state framework extended for unsaturated soils, is based on two independent stress state variables: net normal stress and matric suction (Wheeler and Sivakumar, 1995). A modified state-dependent dilatancy is introduced to account for the effects of internal state, stress level and soil suction. Comparisons between model predictions and experimental results show the model is able to capture some key aspects of engineering behaviour of saturated and unsaturated soil behaviour at various stress paths. Now geotechnical engineers can carry out ‘what-if’ parametric studies
and investigate design proposals using this advanced soil model when it is implemented into a finite element or finite difference program.
