Modeling fractures in rock blasting

A numerical model based on the discrete element is used to investigate the importance of stress waves on the initiation and propagation of radial fractures during the dynamic loading phase of an explosion. An explosion occurring in a two-dimensional rock plate is simulated and the resulting fracturing process is detailed. First, during the pressure rise of the explosive source, a crushed zone is created in the vicinity of the explosion cavity. Then, because of the tensile tail of the propagating pressure wave, radial fractures propagate from the edge of the crushed zone. Different crack velocities were found which varied with respect to crack length. It was seen that the higher the crack velocity the greater the extent of the radial fractures. Tests with different explosive sources have shown that both the size of the crushed zone and the length of the radial fractures depend on their peak pressure and frequency content. Efficient sources, which generate long radial fractures with a small crushed zone, can be obtained with low peak pressures provided that the frequency content is lowered. Finally, when the plate is subjected to uniaxial compression, the fractures align along the main stress axis. In the light of these results, the method proposed here seems to be appropriate to study complex problems involving the creation and evolution of discontinuities. (C) 1998 Published by Elsevier Science Ltd.