Rockburst proneness characteristics of sandstone subjected to pre-stress and fatigue loading

In this study, variable-limit fatigue loading tests at pre-stresses of 25%, 50%, and 75% UCS were conducted to understand the rockburst proneness of sandstone subjected to pre-stress and fatigue loading. Acoustic emission monitoring and high-speed camera were employed to investigate the evolution of rockburst proneness. The results showed that the mean peak strength increased from 81.27 MPa (under uniaxial compression) to 95.26 MPa at the pre-stress of 25% UCS, then decreased to 77.07 and 77.06 MPa at the pre-stresses of 50% and 75% UCS, respectively. With increasing pre-stress, the shear crack proportion increased from 28% to 51%, while the final cumulative AE energy decreased from 40,153 to 35,936 and 33,021, and the multifractal spectrum width narrowed from 1.323 to 1.259. A comparison of six representative rockburst proneness indices with the specimen failure process showed that rockburst proneness first increased and then decreased. The rockburst proneness was mainly influenced by the competition between the pre-stress induced compaction strengthening and the fatigue loading induced degradation.