Rational crushing of mineral raw materials by well charges as a factor of environmental safety of blasting works in quarries

Purpose. Improving the environmental safety of blasting operations in quarries for the extraction of non-metallic and construction materials based on their rational explosive crushing, aimed at reducing the effect of overgrinding, accompanied by the formation of fine fractions of materials and significant dust emissions. The research methodology provided a theoretical analysis of the destruction processes of a rock massif by well charges of explosives on the basis of calculations of shock adiabats of an explosive wave in rocks at different speeds of detonation of explosives. Experimental verification of the identified patterns was performed by assessing the quality of blasting by the particle size distribution of the rock in the collapse. Research results. The scientific and practical task of ensuring rational explosive crushing of materials in quarries with the use of elongated borehole charges has been solved. Mechanisms for the destruction of rock massifs and the peculiarities of the distribution of destruction zones by dispersed composition have been established, which contributes to the reduction of dust emissions into the atmosphere to an acceptable level of environmental safety of blasting operations in quarries. Comparative estimates of the shock load during the explosion of the explosive charge for the main rocks at different levels of the rate of detonation of charges are given. The dependence of the volume of overgrinding rock in the zone of its adjacency to the charge on the detonation velocity of explosives has been established. An experimental verification of the identified patterns in the current quarry by assessing the quality of blasting by the particle size distribution of rock mass in its collapse after experimental explosions with different parameters is done. Scientific novelty. The multiphase process of rock destruction by explosion was investigated by the calculated determination of the parameters of the shock adiabats of the blast wave in different rocks and at different detonation velocities of explosives. It is shown that during the destruction of a rock mass by the explosion of an elongated borehole charge of explosives, several specific zones of destruction are formed, the characteristics of which differ in particle size distribution. The area of controlled crushing is highlighted, where the intensity of rock destruction can be changed by adjusting the parameters of the explosive load and the area of little or almost unregulated crushing. The possibility of managing the process of dust formation and, accordingly, the level of environmental safety of blasting works in quarries for the extraction of non-metallic and construction materials is substantiated. Practical meaning. The identified patterns and provisions to reduce the effect of mineral overgrinding were used in the development of measures to improve the environmental safety of blasting in the quarry, which, in particular, provided an increase in well spacing in the range up to 3.0-3.4 m and reduce specific energy consumption from 1.27 g/cm3 to 0.97 g/cm3.

Oblique waves in steady supersonic flows of Bethe–Zel’dovich–Thompson fluids

Steady self-similar solutions to the supersonic flow of Bethe–Zel’dovich–Thompson fluids past compressive and rarefactive ramps are derived. Inviscid, non-heat-conducting, non-reacting and single-phase vapour flow is assumed. For convex isentropes and shock adiabats in the pressure–specific volume plane (classical gas dynamic regime), the well-known oblique shock and centred Prandtl–Meyer fan occur at a compressive and rarefactive ramp, respectively. For non-convex isentropes and shock adiabats (non-classical gas dynamic regime), four additional wave configurations may possibly occur; these are composite waves in which a Prandtl–Meyer fan is adjacent up to two oblique shock waves. The steady two-dimensional counterparts of the wave curves defined for the one-dimensional Riemann problem are constructed. In the present context, such curves consist of all the possible states connected to a given initial state (namely, the uniform state upstream of the ramp/wedge) by means of a steady self-similar solution. In addition to the classical case, as many as six non-classical wave-curve configurations are singled out. Moreover, the necessary conditions leading to each type of wave curves are analysed and a map of the upstream states leading to each configuration is determined.

Calculation of Shock Adiabats for Materials Undergoes a Phase Transition

We propose a model that allows a single velocity and temperature approximation, and assuming the same pressure for all phases, to calculate the behavior of porous powder mixtures during shockwave loading taking into account the phase transition. Numerical results are compared with available experimental results of different authors to solid and porous media(shock adiabat, double compression shock waves). It is shown that the calculation gives good agreement with experiment for graphite and titanium

The Equation of a State of Porous Mixture of Condensed Substances With Specific Heat the Dependence on the Temperature

The work is devoted to a problem of the description of behavior of multispecies mixtures of various powders under shock-wave loading. At the description of a mixture the model of interacting and interpenetrating continua, the principles of which construction are stated in the monographies of R. I. Nigmatulin, is used. The equilibrium condition is satisfied by conditions of equality of pressure, temperatures and mass velocity of species. The presence of gas inside pores is taken into account. The porous mixture of the several condensed substances in thermodynamic equilibrium is represented as single-phase continuous medium with the equation of a state in the Mie-Grüneisen form, which parameters expressed in terms of the corresponding parameters of the species. The numerical calculations of shock adiabats for porous substances and porous mixtures of the condensed species are performed with use of various models of the equation of a state of a mixture taking into account: a) only elastic pressure and elastic energy; b) both elastic, and thermal terms with constant specific heat of substance and Grüneisen oefficient; c) elastic and thermal terms with specific heat of substance the dependence on the temperature and variable Grüneisen coefficient. The results of computations are compared with experimental data.