Effect of the charge diameter and type of explosive on the size of the overcrushing zone during an explosion

Abstract

When rocks are extracted in building-stone and limestone quarries, in addition to the maintenance of highgrade crushing during blasting, one must reduce the yield of overcrushed rock, which depends on the pressure pulse parameters in the charge chamber, characterized by the rate of increase and value of the maximum pressure, and on the duration of the pressure above this level. We will establish the effects of each of these parameters on the stress field characteristic and the crushing intensity of the rocks.The effect of the rate of pressure increase in the shock wave front on the parameters of the stress field created by an explosion in a medium can be established in an elastic approximation. Such an assumption is perfectly acceptable because the fracture time is much greater than the duration of pressure increase in the charge chamber when commercial high explosives are used. Let us assume that the charge cavity of radius r 0 is located in an ideally elastic infinite area. (The condition of limitlessness is automatically satisfied for all laboratory and industrial explosions, because during the period of pressure increase in the charge chamber the stress wave does not reach the free surface.)The one-dimensional stress wave created by the explosion is represented by a single system of generalized equations:Oa r