Experimental and numerical study of fatigue damage of highly stressed rocks under cyclic loading

The damage and fracture tests of sandstone at different upper and lower stress ratios were performed, and a stress corrosion model based on the particle flow code method was introduced to reflect the fatigue damage process of the rock under cyclic stress. The instantaneous and time-dependent parameters at a mesoscale in the model were calibrated against laboratory tests, and the established time-dependent deformation damage and rupture model comparatively justified. Furthermore, the experimental and numerical tests on rock at various upper and lower stress ratios were performed. The results show that the hysteresis loop in the damage failure curve of the model presents the characteristics of 'sparse-dense-sparse', and the curve presents a convex deceleration rise at the beginning of loading and then develops steadily, and finally, it accelerates up to failure in a step-wise downward convex trend. When the lower limit stress level of the fatigue load is fixed, the higher the upper limit stress level, the larger the area and spacing of the hysteresis loops, the fewer the cycles, and the shorter the fatigue life of the model. When the upper limit stress level is fixed, the higher the lower limit stress level, the smaller the stress magnitude, the smaller the area and spacing of the hysteresis loops, the fewer the cycles, but the fatigue life of the model is almost identical, which indicates that the upper limit stress is one of the important factors affecting the fatigue life of rock. © 2021, Central South University Press. All right reserved.