Purpose. Experimental study and theoretical modeling of conditions initiating destructive processes and development of gas generation in coals.Methods. Analysis, generalization and statistical processing of experimental data and results of analytical studies followed by the identification of patterns, and numerical solution of equations in partial derivatives.Findings. Experimental studies of changes in properties of mechanically activated samples of gas coal and fat coal in weak electric fields have been performed. The experimental results were compared with the characteristics of coals taken from the zones of different outburst hazard probability, which enabled to formulate new ideas about the causes of gas generation in coals. A mathematical model has been elaborated for gas outburst development taking into consideration the solid phase porosity changes due to the transition of coal organic mass to gas.Originality. The treated samples with the broken microstructure demonstrated a significant increase (1.5 -3 times) in the characteristic time of methane desorption and manifestation of electret properties identified by the value of the evoked potential and electrochemical activity, while qualitative and quantitative changes in the treated coal properties were identical to the natural analogues. It is for the first time that the developed mathematical model of gas flow during the outburst reproduces the changes in porosity and permeability of the rock caused by chemical reactions of gas generation by coal organic mass.Practical implications. The improvement of the proposed outburst model can be used for predictive estimations of instantaneous outbursts taking into account the changes in thermodynamic and kinetic stability parameters of the "coal -gas" system.

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The paper shows the estimations of maximal penetration depths of shaped charge jets in a steel armour as a function of stand-off distance to the liner base. The data – in-stantaneous coordinates of positions, masses, and velocities of jet elements were received as results of numerical calculations for selected examples of designs of shaped charges. It was shown that the crater’s depth is a function of acceptable maximal extension of jet elements and their minimal velocity. The results were compared with experimental data.

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