A review of models for predicting the thermomechanical behaviour of soft clays

SUMMARY This paper critically examines the use of the modified Cam clay stress-strain model in predicting the thermomechanical behaviour of soft clays. The equations governing the thermomechanical behaviour of a saturated soil are summarized and their methods of solution are briefly discussed. The observed thermomechanical soil behaviour reported in the literature has been compared with the predictions made using the modified Cam clay model. In making these comparisons, two extensions of the well-known modified Cam clay model have been considered: one proposed by Britto et al.' in which heating induces thermal stresses and strains in the soil but has no direct effect on the work hardening, and the other proposed by Hueckel and Borsetto' in which a change in temperature also affects the yield surface. The comparisons are confined to the behaviour of normally and lightly overconsolidated clays, where the modified Cam clay is known to perform well. Apart from the effect of a single heating-cooling loop, cyclic behaviour is not considered. It is concluded that both models provide reasonable predictions under isotropic stress conditions. Although exhaustive comparisons have not been made for deviatoric stress excursions (because of the lack of experimental data), it appears from preliminary studies that neither model performs particularly well for this form of loading.