Theoretical principles of blasting energy distribution in a medium, and their applications to practical problems

Abstract

In blasting operations it is necessary to determine the type of explosives, the size of the charges, their arrangement in the rock, and the time intervals and order of detonation. In this article we consider the theoretical principles of the process of distribution of the energy of the blast in a medium and their application in determining the spatial arrangement of the charges in grouped blasting. An analytical derivation of the optimum value of the relative spacing, m, characterizing the relative arrangement of the charges, can be made on the basis of the initial and boundary conditions with the exponential law of wave energy distribution in a medium and the main principles of the energy theory of strength. For the practical ranges of initial pressures (4.10/sup 4/-4.10/sup 5/ kg/cm/sup 3/) and rock strength constants (2.10/sup 2/-2.10/sup 3/ kg/cm/sup 2/), the value of m calculated from Eq. (28) ranges from 2.2 to 2.5. The results of the above theoretical investigation of the arrangements of charges in the rock were used in practice in blasting operations, and appreciably improved their efficiency. The scientific and technical literature contains a large number of recommendations (mainly of an experimental nature) on the optimum value ofmore » the relative spacing of the charges: the recommended values vary between one and eight. Our theoretical investigation of the spatial arrangement of the charges shows that the optimum range of m is very much narrower. Experience in a mine confirms the advantages of changing to blasting with m = 2 instead of the previously used m = 4, and this supports the results of our theoretical analysis.« less