Deformation damage and acoustic emission characteristics of red sandstone under fatigue–creep interaction

Abstract

Most engineering rock masses are actually under the interaction of fatigue load and creep load. Currently, the understanding of the fatigue or creep characteristics of rock is relatively mature, but the damage and failure characteristics of rock under fatigue–creep interaction (FCI) are rarely studied. In this study, FCI loading tests were carried out on red sandstone with prefabricated cracks at different angles. The results showed that the elastic modulus tended to be stable with the loading. While the deformation modulus and secant modulus decreased nonlinearly, and a relatively significant decrease occurred after the creep loading. The strain evolution could be divided into deceleration stage (P1), stable stage (P2) and acceleration stage (P3). Creep loading would increase the energy dissipation of the sample, thereby accelerating the accumulation of rock damage. A macro–micro coupling damage model was established, which reflected the damage evolution and strength variation of samples. In addition, acoustic emission (AE) was mainly generated in the fatigue loading stage, and the AE level increased with the increase of the crack angle. The crack propagation process of samples with different angles of crack was analyzed by b value of AE, and the failure modes of samples were further discussed. The research results have certain theoretical reference value for understanding the damage and failure characteristics of fractured rock mass under interaction.