Abstract: According to rock mechanical characteristics of creep deformation at different stages, the visco-elastic-plastic states from deformation to rupture are classified, and the corresponding creep mechanical properties at different states are given. Under the assumption that ductile shear failure occurs in triaxial compression test, the maximum principal strain discriminant for the critical state transformation is derived using Drucker-Prager strain criterion. Furthermore, a visco-elastic-plastic damage evolution model for describing the nonlinear acceleration creep behavior is constructed by introducing a statistical damage factor based on the theory of Perzyna in consideration of the hardening effect in subsequent yield. Moreover, triaxial creep test is conducted with sandstone specimens from the Three Gorges Reservoir area, and the creep deformation curves under different pressures are acquired. Test results show that the creep characteristics of rock specimens are obvious, and non-linear accelerated creep happened under the final stress level. The proposed model is used for the fitting of test creep curves, and the fitting results suggest that the model could accurately describe different stages of sandstone’s creep deformation.

Key words: rock mechanics, visco-elastic-plasticity, creep mechanical tests, damage, constitutive model