A thermo-mechanical constitutive model for fine-grained soils based on thermodynamics

The formulation of a new thermo-mechanical constitutive model consistent with the principles of thermodynamics is presented. The model is capable of predicting the rate-independent thermo-mechanical behavior of fine-grained soils. The constitutive equations are derived by defining only a Gibbs-type free energy and a dissipation potential, in accordance with the hyperplasticity method. The addition of thermo-elasticity to the energy potential, and the embedding of the identified thermo-mechanical mechanisms into a newly proposed dissipation potential, enables the model to describe the thermo-mechanical behavior. The proposed dissipation potential eliminates the application of shift stress, which results in a simpler formulation in the context of hyperplasticity. The step-by-step procedure of deriving the equations, as well as a detailed analysis of the parameters of the model, is presented. The performance of the model is shown to be in good agreement with experimental data. A qualitative description of the possible micro-scale mechanisms for fine-grained soils, when subjected to temperature variation, is presented, as a step towards including the mechanisms in the formulation.