Dynamic response and rockburst characteristics of underground cavern with unexposed joint

The existence of joints poses a challenge to the dynamic stability of underground caverns. To investigate the dynamic response of the underground cavern affected by an unexposed joint, a series of SHPB tests were con-ducted on the marble specimens with a cavern and differently distributed joint, including the cases of joint location dips of 0 degrees, 56 degrees, 90 degrees, 134 degrees, and 180 degrees and the case of no joint. The discrete element method was also adopted to uncover the dynamic failure mechanism of samples. Based on the experimental and numerical results, the effects of joint distribution on the fracturing process, dynamic strength and local stress evolution of un-derground caverns were systematically investigated. The deformation characteristics, failure patterns, rockburst characteristics and rockburst mechanism were identified for different joint cases. The results showed that the joint has limited influence on the dynamic bearing capacity and failure characteristics of the cavern when the dip theta = 0 degrees, 90 degrees and 180 degrees, but it becomes significant when the dip theta = 56 degrees and 134 degrees. Similarly, when the dip theta falls in the range of 56 degrees similar to 134 degrees, the maximum principal stress around the cavern will be significantly affected, but not when the dip theta is 0 degrees or 180 degrees. More specifically, different joint distributions can cause four kinds of rockbursts on the cavern: A) strain rockburst at the roof; B) strain rockburst at the floor; C) slip rockburst of wing cracks at the roof; and D) slip rockburst of wing cracks at the floor. When these rockbursts occur, the displacements of sur-rounding rocks will demonstrate obvious abnormal changes (e.g., characteristic oscillations and sudden changes), and C-type rockbursts generally lag behind A-type rockbursts. In addition, the magnitudes of the strain energy release rate can be identified: D-type rockburst >A-type rockburst >B-type rockburst >C-type rockburst > no rockburst. The findings of this study will benefit the stability analysis and risk control of underground caverns.