Abstract: A nonlinear constitutive model with tension cut-off is developed by use of C++ based on Mohr-Coulomb constitutive model in FLAC. For stresses and displacements of monitored elements or nodes, comparison is conducted between the numerical solutions (including solutions based on Hoek-Brown constitutive model, Mohr-Coulomb constitutive model and defined nonlinear constitutive model) and the analytical solutions (based on Hoek-Brown constitutive model). Validation of the defined nonlinear constitutive model is verified. Strain localization of the surrounding rock of a circular tunnel is modeled using the defined elastic-brittle-plastic constitutive model. The tunnel is excavated after the model is loaded to an equilibrium state. On the condition of symmetric boundary conditions of computational model and homogeneous constitutive parameters, four symmetric V-shaped notches are found; as is consistent with observations in situ and experimental results of rockbursts in a hydrostatic pressure. However, if the very brittle strain softening Hoek-Brown constitutive model is adopted, then symmetrical numerical results cannot be observed.

Key words: Mohr-Coulomb constitutive model, Hoek-Brown constitutive model, nonlinear constitutive model, circular tunnel, strain localization, V-shaped notch