A simple model for tertiary creep in geomaterials.

This paper presents a constitutive modelling approach to the viscoplastic-damage behaviour of geomaterials. This approach is based on the hyperelasticity framework where the entire constitutive behaviour is derived from only two scalar potentials: a free energy potential and a dissipation function. The novelty of the new proposed model, in addition to being thermodynamically consistent, it requires only a few parameters which can be derived from conventional laboratory testing. The model has been specically tested for its ability to reproduce a series of triaxial compression tests on core rock samples. The comparison between the viscoplastic-damage model predictions and experimental results show the model is remarkably successful in capturing the stress-strain response at both peak stress and in the region of material softening and the time to reach failure