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Durham University

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Publication details for Professor Ashraf Osman

Osman, A. S., Birchall, T. J. & Rouainia, M. (2020). A simple model for tertiary creep in geomaterials. Geotechnical Research 70(1): 3–59.

Author(s) from Durham


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.