A novel insight into the transition from plasticity to elasto-damage modelling in intact rocks

This study developed a coupled elasto-damage constitutive model for predicting the transition from brittle to ductile behaviour in quasi-brittle rocks. By integrating the bounding surface framework with damage evolution hardening, the model can accurately simulate the stress–strain behaviour under various loading conditions. Unlike traditional elastoplastic criteria, the proposed model incorporated the inelastic strain from the initial stage of loading and accounts for the associated damage evolution, enabling a smooth transition from elastic to inelastic zones. It can also consider the nonlinear deformation of quasi-brittle rocks with different geological origins under various loading conditions through highlighting the importance of considering damage factor in rock materials modelling. The proposed framework introduced damage-induced permanent deformation as an alternative to plasticity in stress–strain modelling by combining damage and shear effects. Finally, a comparative analysis was performed between the scenarios with and without damage function to highlight the significance of having damage parameter in modelling of quasi-brittle rocks. It is noteworthy that such a model was mainly developed to account for the triaxial loadings and to capture the complex relationship between inelastic hardening/softening and damage progression.