A thermomechanical model for clays

The constitutive modelling of kinematic regions of high stiffness in clays has been performed using various formulations, most of them non-rigorous in terms of Thermodynamics. The purpose of this paper is to set up a thermodynamical-based approach, within a unified hyperplastic/continuous-hyperplastic framework, which ensures that the Laws of Thermodynamics are always obeyed. The advantage of the unified framework is that it enables continuous and abrupt yielding in the same package. As an example, the scheme is applied for construction of a new continuous hyperplastic critical state (CHCS) model that also adopts well-known power dependency of elastic moduli on pressure without violation of the law of energy conservation. The current paper presents the evaluation of the CHCS model against triaxial test data and against experimental data from tunnel excavation using the finite difference technique.