A thermomechanical model for saturated soil at small and large strains

Abstract

Many elastoplastic models have been developed for simulating thermomechanical behaviour of saturated soil. Although the yield surface of these models shrinks with temperature, its shape is always assumed to be independent of temperature. This simplification may induce errors in predicting thermal effects on shear behaviour. Furthermore, existing models tend to focus on thermomechanical behaviour at large strains. Behaviour such as the degradation of the shear modulus with strain at small strains (<1%) is often ignored. To address these issues, a new thermomechanical model is developed using the bounding surface plasticity theory. Both the size and shape of the bounding surface are allowed to change with temperature. The new model is able to predict elastoplastic response of saturated soil at small strains, even when stress path is within the bounding surface. Using this new model, thermomechanical behaviour of four different soils having different overconsolidation ratios is simulated. Comparisons between measured and computed results reveal that the new model is able to capture many vital aspects of thermomechanical behaviour, including volume changes during heating and cooling, and thermal effects on drained and undrained shear behaviour. In particular, it predicts a gradual degradation of the shear modulus at small strains. By incorporating thermal effects on the shape of the bounding surface, the modelling of thermomechanical behaviour, especially the effective stress path during undrained shearing, is improved.