Research on the energy evolution law and acoustic emission characteristics of rocks subjected to cyclic loads: From the perspective of characteristic stress

Sandstone is a common rock material in engineering, surrounding rock, such as tunnel surrounding rock and mining roof, and is often subjected to cyclic loads. Systematically studying the mechanical behavior of sandstone under cyclic loading under different confining pressures and exploring its precursor information of fractures is of great significance for guiding engineering design and improving the accuracy of disaster prediction. Based on this, this paper conducted cyclic loading and unloading experiments on sandstone under conventional triaxial loads, synchronously collecting mechanical data and acoustic emission (AE) signals during the process, in order to establish a connection with the progressive failure process of rocks and provide a theoretical basis for the smooth development of rock engineering. The research results indicate that (1) the energy evolution of sandstone under cyclic loading exhibits significant periodic changes, which are closely related to the four stages of crack propagation. (2) The stable variation of average AE energy corresponds to the crack closure stage and elastic deformation stage, while the rapid increase in average AE energy corresponds to the stable and accelerated crack propagation stages. (3) High frequency AE events occur when the degree of rock damage is significant. (4) The variation pattern of the ratio of average tensile AE to shear AE is closely related to the crack propagation state of the rock and is significantly influenced by the confining pressure.