Display of mechanical stresses' distribution in mining areas in the intensity dynamics of the Earth's natural pulsed electromagnetic field

The purpose of the research is to substantiate the theoretical prerequisites for the interpretation of the geophysical method of the Earth's natural pulsed electromagnetic field (ENPEMF). The justification will be performed by quantifying the stress state of the rock massif, modeling of the obtained analytical dependencies for disturbed massifs. The basis for the interpretation is the coordination of the obtained distributions of intensity with the intensity of the electromagnetic field. The initial data are classical formulas of theoretical mechanics, modified to the conditions of the geological structure of the object of research and long-term research by the method of ENPEMF at the object – Kalush-Golynsky potassium salt deposit in the Pre-Carpathian. The research methodology included the development and presentation of models of the stress-strain state of the mining area, followed by the calculation of specific distributions of stress and analysis of their relationship with the dynamics of ENPEMF for specific areas of regime observations. The results of the research are given in the following sequence: 1) an example of calculating model stresses; 2) practical results of ENPEMF; 3) comparison of theoretical model calculations and real observations' data. Examples of calculations are given for a rock massif including a rectangular-shaped mining operation located in a salt formation. The distribution of stresses is calculated for the 2D model, taking into account the actual physical parameters. The series of graphs shows the change in tension both along the profile and with depth. The model is complicated for a variant of two chambers located at different depths. Observation of ENPEMF is demonstrated for a complex section of rocks. Actual plots of the field intensity with a high degree of correlation correspond to the calculated plots at a certain depth. The complication of the section and the presence of different stages of the postoperative period, which is reflected in the regime observations, leads to the deviation of the form of the graphs from the "ideal-model", but at the qualitative level this form corresponds to the theoretical one. The novelty lies in the development of the principles of quantitative assessment of the stress-strain state of the disturbed rock mass as the basis for the theoretical assessment of the distribution of the natural pulsed electromagnetic field of the Earth. In particular, the identity of the results of practical geophysical observations and computational models of the stress-strain state is demonstrated. The results obtained should be considered as a contribution to the theoretical basis of the quantitative interpretation principles of the geophysical method of ENPEMF. At the same time, the ways of further research for the full implementation of this research area are indicated.