Determination of the blasting load variation in borehole

• 1、State Key Laboratory of Water Resources and Hydropower Engineering Science，Wuhan University

Abstract：The determination of the blasting load is the basis and presupposition for dynamic analysis of blasting in which semi-empirical blasting load curves are always employed. A theoretical variation process of the blasting load in the borehole was calculated through the analysis of the dynamic expansion of the borehole volume，the development of fracture in radial direction and the movement of the stemming in axial direction after explosion, in accordance with the calculation of the outburst of explosive-produced gases based on one-dimensional nonsteady flow. The results indicate that the high pressure of gases in borehole after initial expansion drop down to a lower level through the spread of rarefaction wave and reflected rarefaction wave, and with a faster rate and short duration for the first attenuation. Different isentropic indexes mainly affect the attenuation rate of the first stage, and the greater the isentropic index is, the faster the attenuation rate is. The blasting load distributed along the borehole axis during attenuation is unequal and increases gradually with the depth. But the degree of uniformity would gradually reduce with time, and then the pressure along the whole borehole tends to equality eventually.

Keywords： mechanics of explosion blasting load one-dimensional nonsteady flow explosive-produced gases pressure attenuation