Abstract: Damage characteristics and damage evolution mechanism of post-peak fractured rock mass are critical for controlling the stability of surrounding rock in underground caverns, tunnels and other rock engineerings. Since the current study on damage and destruction characteristics of post-peak fractured rock mass is insufficient, and its understanding is not comprehensive, the potential engineering accidents may occur, such as large collapse and large deformation. In this study, a series of triaxial tests was carried out to investigate mechanical properties of the post-peak fractured rock mass. Then, the corresponding nonlinear damage characteristics were analyzed. Assuming that the rock damage satisfies the Weibull distribution rule, a constitutive equation of the fractured rock was deduced by introducing a damage variable. A nonlinear damage and failure criterion of post-peak fractured rock was established by combining with the energy dissipation principle and strain energy density theory. Based on the above principle, the calculation program of damage failure of post-peak rock was developed according to FISH language, and the simulation of the non-continuous process of post-peak fractured rock was realized using a continuous method. As a result, the damage and failure characteristics and its evolution rule of post-peak fractured rock mass were revealed. Furthermore, numerical results were compared with triaxial compression results. It turns out that the constitutive equation and the discriminant criterion can well simulate the nonlinear damage and rupture process of fractured rock. Therefore, this study can provide a new theoretical analysis method to effectively control the stability of surrounding rock.

Key words: nonlinear damage, strain energy density theory, post-peak strength, numerical simulation