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 r adial fractures during the dynamic loading phase of an explosion. An e xplosion occurring in a two-dimensional rock plate is simulated and th e resulting fracturing process is detailed. First, during the pressure rise of the explosive source, a crushed zone is created in the vicini ty of the explosion cavity. Then, because of the tensile tail of the p ropagating pressure wave, radial fractures propagate from the edge of the crushed zone. Different crack velocities were found which varied w ith respect to crack length. It was seen that the higher the crack vel ocity the greater the extent of the radial fractures. Tests with diffe rent explosive sources have shown that both the size of the crushed zo ne and the length of the radial fractures depend on their peak pressur e and frequency content. Efficient sources, which generate long radial fractures with a small crushed zone, can be obtained with low peak pr essures provided that the frequency content is lowered. Finally, when the plate is subjected to uniaxial compression, the fractures align al ong the main stress axis. In the light of these results, the method pr oposed here seems to be appropriate to study complex problems involvin g the creation and evolution of discontinuities. (C) 1998 Published by Elsevier Science Ltd.