Influence analysis of persistent joint on single-hole blasting damage of rock mass

It is difficult to be measure and analyze the blasting damage of rock masses containing persistent joint. A field test was conducted to determine the distribution range of blasting damage zone in intact rock mass for investigating the macroscopic characteristics of blasting damage of rock masses containing persistent joint and effectively predicting the damage scope. The effectiveness of the numerical calculation was verified by combining the calculation of blast load using finite element ANSYS/AUTODYN software and the calculation of blasting damage zone of rock masses using discrete element UDEC software. Typical numerical calculation models of persistent joint passing through the upper, middle, and lower parts of the blast hole were constructed to investigate the distribution laws of blasting damage zone in rock masses under the joint dip angles of 0°, 15°, 30°, 45°, 60°, and 75°. Results indicate that the distribution pattern of blasting damage zone is significantly affected by existence of persistent joint. The maximum blasting damage width under a small joint dip angle is approximately 1.8 times that under non-joint condition. The maximum blasting damage depth under a large joint dip angle is approximately 2.3 times that under non-joint condition. Under the special circumstance in which the joint with the dip angle of 90°, the joint nearly has no influence on blasting damage width but remarkable influence on blasting damage depth.