Abstract: The implementation of an anisotropic damage constitutive model in FLAC^3D for hard rock is presented in this paper. An incremental form of elastoplastic-anisotropic damage constitutive equation is first deduced using the plastic mechanics theory and the elastoplastic-damage constitutive theory within the framework of thermodynamics of irreversible process. Meanwhile the concrete form of evolution rate of damage tensor is determined by the consistence condition of damage criterion. On the basis of these formulas,the detailed flowchart of numerical calculation by using the elastoplastic-anisotropic damage model and M-C yield criterion is established and some details the numerical calculation are also discussed. A DLL(Dynamic Link Library) file corresponding to the elastoplastic-anisotropic damage model is written to be called by the FLAC^3D software. The uniaxial and triaxial compression numerical tests of cylinder sample are then conducted to test the validity of this user-defined model. The results show that this model is capable of describing the nonlinear behavior of hard rock. The validity of elastoplastic-anisotropic damage model in practice is further tested by applying it to a numerical simulation of staged excavation of a fictitious underground opening. Result show that the highly damaged zone around the opening determined by the simulation is in agreement with the actual observation in project area. The result also show that using the tensile strain tensor to measure damage and establish damage criterion grasps the nature of hard rock damage.

Key words: thermodynamics of irreversible process, elastoplastic, anisotropic damage, FLAC^3D, constitutive modelabout