Effects of confining pressure on acoustic emission and failure characteristics of sandstone

In this study, uniaxial and triaxial compression acoustic emission (AE) tests were implemented to investigate the AE effect and failure characteristics of sandstone under different confining pressures (σ3). The evolution of AE parameters in the rock failure process and fracture fractal dimension characteristics after failure were analyzed. The results revealed that the activity of the AE signal is strongly related to σ3. The evolution of the Ib value can be divided into the I-fluctuation, II-stability, and III-decrease stages. In the first stage, the Ib value of the AE was relatively high, and the AE energy was low. Then, the Ib value tended to be stable; however, the fluctuation amplitude decreased, and the AE energy rapidly increased. In the stage of decrease, the AE energy sharply increased before the load approached the peak value, and the Ib value significantly decreased and dropped to the lowest point before the peak value. As σ3 increased, the rock’s failure mode changed from tensile failure to shear failure and became more coordinated. As the confining pressure increased, the shape dimension decreased, and the order degree of rock failure increased. The confining pressure exerted a certain control effect on the rock failure.