Abstract: Based on the often neglected problem of disturbance of explosive load to the defects of surrounding rock in adjacent tunnel back-blasting side, using explosion load digital laser dynamic caustics experimental system，the slant crack propagation regularities of neighboring roadway side are explored under explosion dynamic load. The experimental results show that crack extension final displacement is the largest, when the angle of prefabricated crack is in the side of back blasting of the straight wall and arch tunnel is 30° under the blasting load, then with the increasing or decreasing of crack angle, the ultimate displacements of crack extension all tend to decrease gradually; attenuated effect for stress wave of arc is less than the rectangle. Consequently, oblique upward crack extension displacement is 2-3 times of oblique down crack which is symmetry with horizontal subjected to blasting loading. In addition, energy release rate has driving effect on the propagation of the crack, and the energy release rate reaches the maximum in a moment and then gradually decreases to zero. But this change range becomes small with the crack extension displacement decreasing. The research provides theory basis for the economic and reasonable supporting of adjacent tunnel back-blasting side.

Key words: blasting dynamic load, neighboring roadway, inclined crack, dynamic caustics, energy release rate