Effect of Confining Pressure on the Damage Evolution and Failure Behaviors of Intact Sandstone Samples During Cyclic Disturbance

Under cyclic disturbances, the free faces of the surrounding rock that simultaneously bears a high geostress may pose potential engineering hazards related to large deformation or displacement. However, the mechanism for the damage and failure of the rock under coupling conditions of triaxial stresses and cyclic disturbance remains elusive. The primary objective of this study was to investigate the effect of confining pressure on the damage evolution and failure behaviors of intact sandstone samples during cyclic disturbance. A series of tests with a continuous axial cyclic loading in triaxial stress states were performed on intact red sandstone samples. Five levels of confining pressure (0, 10, 20, 30, and 40 MPa) were applied during axial cyclic loading at a 10 Hz frequency and a 2.5 MPa amplitude. The mechanical responses, damage evolution, and failure results were obtained, and the mechanism of the sudden jump in stress at the end of the cyclic disturbance phase was analyzed based on the cusp catastrophe theory and a proposed mechanical model for the rock-test machine system. According to our experimental results, both the duration and the number of cycles are positively correlated with the confining pressure, which impedes the formation and growth of cracks in the rock samples and reduces the degree of damage during cyclic disturbance. Furthermore, the damage variable of the rock samples, which was defined using the maximum strain method, initially increased dramatically with a steep slope, and then, it increased slowly with a gentle slope. As the confining pressure increased, after the cyclic disturbance tests, the rock samples exhibited increasing amounts of flaking and exfoliation. The obtained results increase our understanding of the mechanism of cyclic disturbance-triggered damage and failure of rocks and may help improve the design and construction level and reduce disturbance-triggered engineering disasters in the future.

Automated summary

The study investigated the effect of confining pressure on damage evolution and failure behaviors of intact sandstone samples under cyclic disturbance. It was found that both the duration and number of cycles positively correlate with confining pressure, impeding crack formation and reducing damage during cyclic disturbance. Increasing confining pressure resulted in more flaking and exfoliation of rock samples after the cyclic disturbance tests.