Acting law of in-hole initiation position on distribution of blast vibration field

Abstract

In rock drilling and blasting, the in-hole initiation position determines the propagation direction of the explosive detonation wave, and thereby affects the distribution of blast vibration field (BVF). In this study, the acting mechanism of the initiation position was investigated via the comprehensive analysis of the distribution of the detonation products, the explosion energy as well as BVF of the cylindrical charge. Then, the distribution law of BVF under different initiation positions was analyzed using the Heelan’s short-column-solution based superposition model of an extended charge. At last, the acting effect of the initiation position on the distribution of BVF was demonstrated by the onsite blasting experiment. Results indicate that the acting mechanism of the initiation position lies in the axial non-uniform distribution of the explosive energy and the phase delay effect of the superposition of BVF. The in-hole initiation position has the adjustment effect on the distribution of BVF, due to which, the blast vibration amplitude is strengthened at the forward direction of the detonation wave. It needs to be pointed that the non-uniformity of the distribution of BVF is under some control of the explosive length and the explosive velocity of detonation. For the common initiation modes, the field test results indicate that the ground peak particle velocities under the bottom are larger than those under the top and mid-point initiations, and the top initiation is the smallest. Besides, the blast vibration differences becomes more obvious as the blast-hole depth increases, but the vibration difference gradually vanishes with distance.