Experimental Investigation on Rockburst Energy Characteristics of True Triaxial Unloading in Sandstone Under High Stress

To explore the energy evolution characteristics of rockbursts and the mechanism of excess energy in rockbursts, a self-developed rockburst experimental system was used. We performed true triaxial rapid unloading rockburst simulations and triaxial experiments based on the complete stress-displacement surface (CSDS) model prediction of the post-peak curve of rock uniaxial compression. By analyzing the characteristics of stress–strain curve and energy evolution of the rockburst experiment and comparing the energy storage characteristics of the two experiments, we arrived at the following conclusions Unlike the static failure of rock due to uniaxial compression, the occurrence of rockburst is mainly due to the generation of excess energy, which depends on the elastic strain energy stored before rock failure, outside energy input after rock failure and residual elastic strain energy. The intermediate principal stress of the rockburst experiment stored considerable residual elastic strain energy after the rockburst, resulting in an insufficient release of the elastic strain energy stored before the rockburst. The intensity of the rockburst is closely related to its excess energy release rate (EERR). With an increase in the EERR value, the cumulative energy of acoustic emission (AE) during rockbursts, the fractal dimension of rockburst fragments, and the rockburst intensity gradually increase.