Effect of prestress on propagation of blasting-induced main crack in specimens with empty hole

Abstract

In-situ stresses have a significant effect on blast results in deep rock mass. In this paper, firstly, the effect of a prestress (similar to an in-situ stress) on the propagation of blasting-induced main crack in the specimens with an empty hole was studied by dynamic caustic method, considering reflected stress wave. Then, the effect of prestress on the stresses around the empty hole during blasting was studied using numerical analysis. The results show that the prestress can significantly increase (1) the hoop tensile stresses on the upper and lower side of the empty hole, (2) the length of the main crack, (3) the dynamic stress intensity factor (DSIF), (4) the propagation velocity of the main crack, and (5) the crack arrest time when the prestress is parallel to the co-axis direction of the empty hole and the blasthole. Moreover, the prestress promotes the attenuation of DSIFs in the early stage of blasting and limits the increase of DSIFs under vertical reflected stress wave. The lower side of the empty hole is easier to be fractured than that of the upper side. Meanwhile, the peak compressive hoop stress on the upper side of the empty hole does not appear closest to the empty hole.