Based on theories of explosive mechanics and rock fracture mechanics, the influence mechanism of rock strength on the\npropagation length of the primary crack in the directional fracture blasting with slotted cartridge has been investigated deeply to\npropose the relation equation between the rock strength and the propagation length of the primary crack. Theoretically, the\nmaximum length a^m of the primary crack increases with the enhancing rock strength parameters. The explicit dynamic analysis\nsoftware LS-DYNA has been used to simulate the slotted cartridge blasting in the mudstone, sandstone, and granite with different\nstrengths in order to reveal the effect of rock strength on the propagation length and velocity of the primary crack and the stress\ndistribution characteristics in rock. The numerical results show the primary crack easily bifurcates and attain a much shorter\npropagation length in the mudstone with the minimum strength, and there are radial cracks appearing in the nonslotted direction.\nWhen rock strength rises, the propagation length, velocity, and duration of the primary crack and the concentration degree of\neffective stress in the slotted direction will all increase in the sandstone and granite, but there is an opposite influence trend of rock\nstrength in the stage of the initial guide crackâ??s formation. The cracking velocity has an overall oscillation downtrend whose swing\namplitude enhances clearly with the increasing rock strength, signifying the more unsteady propagation of the primary crack in\nthe higher strength rock.
Loading....