On the basis of the algorithm computed the parameters of the force fields for the various options of instant and delayed explosion system of concentrated charges. Calculations of the marginal effects by the explosion of a borehole charge with limited size suggests that assuming instantaneous initiation of the charge in both ends of the charge degeneracy of the axial symmetry of the force field occurs from the ends of the charge to a depth of 50 its radii, that is, in real terms short of blasting borehole charges of their mechanical effect in a greater degree is formed by the weakened end sections of the linear charge.
To compensate for the energy losses at the initial stage of development of the force field fuse degeneration of the wave front strain it is possible to increase the end part of the borehole charge of 1.5...1.7 times. As a rational method of management of energy flow in the lower end of the charge the proposed application of the intermediate initiator, located at the bottom of the borehole and able, along with the initiation of detonation in the charge to create the conditions for the emergence and development of radial cracks in the plane of the soles of the ledge with the goal of addressing a problem overdrilling. In particular, the proposed replacement of the cylindrical shape of the action tapered, designed for the concentration of energy flow normal to the inclined lateral surface of a cone in the corner area of the bottom of the borehole. Analysis of the results of computer simulation of explosion of the charge in the form of a truncated cone showed that the conical explosion of action generates a force field, pear-shaped, capable to provoke the development of radial-circular cracks at the level of the soles of the ledge, which eliminates overdrill. Made in modelling experiments indicate the possibility of obtaining the embryo of a radial deformation process of the explosion of bottom of action, and engineering calculations the configuration of the zone of destruction from the explosion of the combined charge (conical initiator in charge of explosive) at the lower end of the borehole indicate a forward lateral effects of the explosion in the direction of the plane of the soles of the ledge. While the rational angle of the side surface of the inverse conical charge to its larger base is 70О ...80О.
The analysis of calculation data shows that the volume pruinosae region-level array of tamping between adjacent craters does not practically depend on the height of the step. However, in absolute terms this volume decrease with decreasing of charge diameter up to 105 mm, network charges 3х3 m and with ussng of industrial explosives type ANFO. These parameters can be considered the most rational for the design of blasting networking in terms of quartzitic rocks developing on mountain slopes.
Due to the lower initiation during detonation of the charge in the array radiates the shock wave front in space between adjacent charges is oriented towards the surface layers at the level tamping. The greatest effect of such a reorientation of force fields can be achieved simultaneously by the lower initiation of adjacent borehole charges. Then the fronts of the stress field needs to meet in space between adjacent charges, and the total vector force field is directed normal to the upper free surface of the block. In fact, in this case, a scheme of the vertical V-cut, oriented instead of of the side surface to the side of the roof ledge, which through its significant stretch is one of the main sources of oversizes.
The paper proposes a fundamentally new scheme of interaction of groups of charges, which contradicts the traditional methods of designing explosive networks. A complex switching scheme is implemented, which is realised as follows. Three adjacent rows of downhole charges are combined into one joint group for simultaneous parallel burst; the following groups of 3 adjacent rows each iniciated with short delays. The implementation of such scheme allows to use the mechanism of movement of rock masses in the vertical direction with the traditional collision of areas of the array in the horizontal direction. The benefits of using a mixed network switching scheme have been proven by industrial testing. The proposed scheme is accompanied by the application of advanced contour blasting technique.
As a result of the introduction of advanced parameters of designing charges woth limited length and the scheme of their massive blasting, the enterprise completely abandoned the overdrill at the gold-bearing Chovdar field recommended in the dissertation. This allowed for a 10% reduction in the amount of drilling work and the consumption of explosives, materials and labor, and also reduced the output of the oversized fraction by half (from 10 to 5%).
