Experimental Investigation of Rock Burst Failure Characteristics in Red Sandstone with Dual Fractures under True Triaxial Conditions

Rock bursts have become a significant geohazard in the construction of underground engineering that cannot be ignored. This study conducts true triaxial five-sided loading tests on red sandstone containing different pre-existing fractures, with one side free, and utilizes a high-speed camera system and acoustic emission (AE) monitoring system to compare and analyze the mechanical characteristics of stress-strain, the development process of rock bursts, the morphological damage characteristics of the parent rock, and the evolution characteristics of AE for samples with different fractures. The results indicate that: (1) The elastic modulus, peak stress, and peak strain of rock with different fracture dip angles exhibit a trend of initially decreasing, then increasing, and finally weakening as the fracture dip angle increases. Conversely, the damage coefficient shows an opposite variation pattern; (2) The dynamic process of ejection for different fractured samples mostly goes through three stages: the rock particle ejection stage, the rock fracture stage, and the overall rock failure stage; (3) The failure mode of different parent rocks is characterized by tensile failure due to tensile action near the free surface and its surrounding area, while the failure feature away from the free surface is mainly shear failure due to shear action. Moreover, the interaction between fractures increases with the increase of fracture dip angle; (4) During the continuous loading of external stress, there will be a period of extreme value jump in absolute energy and the number of AE hits, which corresponds to the rock burst damage stage of the rock. This research provides a theoretical basis for the occurrence law of rock burst disasters in goaf areas with complex fracture network systems and is of great significance to engineering construction.