and a high degree of mechanization. The annual mineral output of a single enterprise reaches 30-40 million tons of ore or coal, and the total amount of processed rock, including stripped overburden, reaches tens of millions of cubic meters.The principal method of detaching hard rock and preparing it for further processing is blasting: this involves the problems of breaking down the rock and simultaneously crushing it to fragments with sizes and positions which will maximize throughput and minimize wear in the loading, transportation, and crushing equipment.The quantity of explosives used by a single mining enterprise amounts to 15-20 thousand tons per annum, and the quantity used in simultaneous blasting is 1300 tons. These scales require safe explosives and necessitate mechanizationoftheiruse. However, the development of mechanization in blasting has lagged behind the growth in output and behind the mechanization of other mining processes; charging has been mechanized (most completely in underground extraction faces), but very laborious manual processes remain in loading and deloading, storage, and delivery of explosives. Only in some individual mining enterprises [Leninogorsk, Sevemyi GOK (Krivbass)] has a start been made on combined mechanization of blasting, including reception, transportation, storage, delivery, and charging.

The optimum choice of the explosive to be used for blasting is of great importance in mining. Its selection should take into account the physical properties of the explosive (its aggregate state, hygroscopicity, consolidation, and compressibility) because they determine whether it will match the task in hand. We must also take into account the blasting properties: the capacity to receive and transmit a detonation, the critical diameter and critical density, the detonation velocity, the volumes of gaseous detonation products, and the explosion temperature. Such properties also include the explosive's sensitivity to mechanical and thermal impulses, which determine the danger of handling, and the extent to which the explosive lends itself to mechanization of mining operations.However, as far as the solution of engineetingprQblems is concerned, the most important blasting properties are those determining the energy of the explosion, i.e., the volume and degree of fracturing (breaking down) of the rock by the explosion. "the criterion for assessing the blasting properties of an explosive must be quantitative,so that it can be introduced directly into calculations of the sizes and arrangement of charges. This eliminates the need for conversion coefficients for assessing the comparative efficiencies of different explosives. Such a quantitative characteristic can be very helpful for characterizing the blasting properties of new, untried explosives.At present the most important practical criteria for assessing the blasting properties of commercial explosive are: the fugacity index (the "efficiency index") expressed by the expansion of a hole in a lead block due to the explosion; and the brisance, which is measured by the compression of a lead cylinder due to the explosion of a standardized sample of the explosive.Both of these are relative indices; but being fairly suitable for comparing the blasting properties of commercial explosives, in the optimum case they may be used for calculating conversion coefficients. However, evenwithin these limitations their use has given rise to objections on the grounds that lead does not simulate the properties of rocks. A test for the fractionation capacity of an explosive has been proposed, based on the degree of fractionation of a block of rock or concrete by the explosion; the aim is to use the results for calculating conversion coefficients.From the theory of explosives [1], it is known that the maximum possible work done by adiabatic expansion of explosion products (the explosive's potential) can be taken without serious error to be equal to the explosion energy expressed in thermal or mechanical units. The total work of an explosion relative to the heat of the explosion (the explosion's efficiency) depends on the ratio of the thermal capacity of the detonation products at constant pressure to that at constant volume. For a farily wide range of commercial explosives, it varies theoretically from '/2.4 to 83.'/90 (mean 78a/o, i8~o); in practical measurement of explosives, such a lev...