Coupled effects of non-persistent joint strike and dip angle on rockburst behavior of granite under true triaxial stress conditions

Rockburst is a serious dynamic hazard in deep underground excavations and is strongly influenced by geological discontinuities. However, the effects of non-persistent joints with different dip angles and strike directions on rockburst behavior remain insufficiently understood. In this study, improved true triaxial tests with one free face and five loading faces were conducted on granite specimens containing prefabricated non-persistent joints with dip angles of 0°, 30°, 45°, 60°, and 90°, and joint strike directions parallel to σ 2 and σ 3 . The results show that the dip angle and strike of non-persistent joints lead to distinct rockburst responses. When the joint strike is parallel to σ 2 , all specimens exhibit rockburst ejection, and the rockburst intensity shows a “U-shaped” distribution with increasing dip angle, reaching a minimum at 30°–45° and a maximum at 90°. Moreover, for joint dip angles of 0°–60°, rockbursts in specimens with joint strike parallel to σ 2 exhibit higher ejection kinetic energy than those in specimens with joint strike parallel to σ 3 . Conversely, at a joint dip angle of 90°, rockbursts in specimens with joint strike parallel to σ 3 exhibit higher ejection kinetic energy than those in specimens with strike parallel to σ 2 . A critical dip angle of about 60° is identified, beyond which the kinetic energy of ejected fragments increases rapidly. These findings improve the understanding of rockburst behavior in rock masses containing non-persistent joints and provide guidance for rockburst risk evaluation in deep underground engineering.