Development of nonlinear constitutive model based on Mohr-Coulomb constitutive model and its application to strain localization

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.