Abstract: Based on damage mechanics and the concept of damage threshold, rock behaves elastically at the beginning of loading, and successive damage is followed when the stress reaches the yield state. Until rock is completely damaged, the stress-strain curve shows deformation characteristics of residual strength. In this study, three-parameter Weibull distribution function is adopted to describe the evolution of rock damage. Meanwhile, the Lemaitre strain equivalence hypothesis is modified by considering the friction force caused by the relatively slipping deformation of rock along pre-existing local cracks. Finally, a new constitutive damage model is proposed to precisely describe deformation characteristics of residue strength and the elastic deformation at the low confining pressure. Furthermore, the proposed model is also verified by experimental results, which indicates that the model can be widely applied to practical engineering projects.

Key words: damage threshold, three-parameter Weibull distribution, Lemaitre strain equivalence hypothesis, residual strength, constitutive model