Abstract：Based on the creep experimental data of shale，the relationship among stress level，time and viscoelastic deformation disciplines of rock is analyzed. One-dimensional viscoelastic creep equation of rock is given by back analysis method. According to theoretical and experimental data，large errors will be encountered without considering time-dependent behaviors of the parameters. Therefore，a non-stationary viscoelastic constitutive model can more accurately reflect the deformation behaviors of rock than those of stationary mode. The necessity of non-stationary parameters is testified. In practical cases，the surrounding rocks in a certain tunnel are supposed to be viscoelastic and visco-elastoplastic bodies，respectively；and certain parameters of rocks are regarded as time-dependent variables. By using back analysis of displacement，two-dimensional non-stationary creep constitutive model of the surrounding rock is identified based on measured displacements. The result indicates that the visco-elastoplastic model with non-stationary parameters can reflect the characteristics of rock mass objectively.
