Abstract: To clarify the creep damage mechanism of rock mass under the periodic variation of reservoir water level in the hydro-fluctuation belt, by considering the weakening effect of the water-rock interaction on the bond and the variation of material properties with time, we proposed a new discrete element method based on the parallel bond model in particle flow code (PFC) and implemented the creep simulation of water-rock interaction based on laboratory tests. The results indicate that under the failure stress level, the micro-crack growth behavior of the samples is similar to the creep strain and it consists of three stages: attenuation growth stage, stable growth stage, and accelerated growth stage. The ratio of the accelerated growth stage’s time to the total time of the micro-crack growth process increases with the period of the water-rock interaction. When the sandstone is damaged in the creep process, the proportion of shear cracks gradually increases with the period of the water-rock interaction and the distribution of inclination angles of micro-crack gradually scatters. The micro-cracks in the areas near the inclination angles of 65° and 115° increase, the tensile strength of the samples weakens and the shear strength increases. Under the water-rock interaction, the maximum cementation energy stored in the samples decreases and the strain with the same cementation energy stored in the samples increases, which is consistent with the rules observed in the field that the overall bearing capacity of the rock mass decreases and the deformation of rock mass increases. Because the method is feasible to simulate sandstone creep process under water-rock interaction, the study can provide theoretical support for the model study of reservoir bank slope rocks under the influence of reservoir water level fluctuation.

Key words: rock mechanics, water-rock interaction, creep test, discrete element method, meso-parameter deterioration