Simulation of overcrushing pressure in coal

Abstract

622.235.5 In blasting by means of elongated cylindrical charges with annular air gaps, the radii of the zones of fracture rf and overcrushing r c, other conditions being constant, depend on the gap width h.In this article we attempt to determine the pressure Pc at the front of the compression wave in the solid rock corresponding to the boundary of formation of a zone of overcrushing. For this purpose we propose a system of dimensionless model parameters which are equal for coal and the model material so that we can use the model to simulate the processes of coal crushing in laboratory conditions. From the experimental results it will be possible to estimate the dependence of Pc on the external conditions of loading.The pressures developed in the coal and rock during blasting from boreholes are much less than the threshold values for melting and evaporation, which according to Arkhipov and Stepanov [1] reach hundreds of kilobars. Therefore, the model parameters determining the processes of fusion and evaporation, were not taken into acccount. The other parameters were chosen as in [2,3]. We took account of the similarity in blasting with a counterpressure ~, the charge shape, and the energy emission determined by the composition and weight of explosives. The final dimensionless parameters of the model were reduced to the system PoUo 2Po;(Pl ~1!~. co. Gt I ~