The mesoscopic deformation and failure mechanism of quasi-brittle rock is that the microcracks initiate, develop, and coalesce to form macrocracks, leading to rock materials final failure. Based on the Mohr-Coulomb criterion, an elastoplastic localization damage constitutive model is built by considering the localization damage evolution. The strain hardening and softening behaviors of rock are described by the expansion and contraction of yield surface with the damage evolution as an inner driving variable. The acoustic tensor is taken as the onset condition of localization damage and damage evolution is defined by an exponential damage criterion in the process of rock fracture. The numerical implementation scheme of the model is introduced according to the return mapping algorithms. The validity of the proposed model is proven by comparing the numerical simulation results with the triaxial test data of Beishan granite and fine-grained sandstone. The results indicate that the model can better capture the main nonlinear deformation characteristics of brittle rock in loading condition, and the post-peak strain softening phenomenon is caused by the rapid increase of the localization damage. Therefore, the proposed model can reflect the localization deformation and failure characteristics of quasi-brittle rock. And the related research work can provide a new idea for the theoretical research of deep rock engineering.

quasi-brittle rock,Mohr-Coulomb criterion,constitutive model,localization damage,constitutive integral algorithms