Assessment of the Impact Hazard of the Array Taking Into Account the Geological Features of the Structure of Electric Profiles

. The current geodynamic situation at the Tashtagol iron ore Deposit is considered. The impact hazard of the array was determined using electrometric coefficients obtained taking into account the geological structure of the array. An assessment of the correspondence of the obtained coefficients to actually registered geodynamic phenomena was made.


Introduction
The experience of mining all ore deposits in Western Siberia shows that with increasing depth of mining operations, there is an increase in the intensity and frequency of manifestations of mountain pressure in a dynamic form. The most representative in terms of manifestations of dynamic phenomena is Tashtagolskoe field.
A total of 595 events with an energy of more than 100 J were recorded at the Tashtagolsky mine during the period from February 2018 to August 2019 within the horizon (-350), with more than 70% of them occurring below the horizon (-300). Their distribution by month and energy class is shown in table 1. At the same time, during the period under review, there is an increase in cases of mountain pressure manifestations in the workings, and there is an increase in energy and the approach of the foci of events to the workings. February 2018  27  4  1  ----32   March 2018  6  ------6   April 2018  8  2  -----10   May 2018  4  3  1  ----8   June 2018  9  6  2  1  ---18 At the same time, during the period under review, there is an increase in cases of mountain pressure manifestations in the workings (table 2), and there is an increase in energy and the approach of the foci of events to the workings. Currently, at the mines, in particular, at tashtagolskoye, for the regional forecast of the degree of impact hazard of the array, it is carried out mainly by methods of Electrometry and microseismics. The foreign experience of recent years is mainly limited to the coal deposits of China and Poland [1][2][3][4][5][6][7][8][9][10] and is based on the study of similar individual issues, while focusing on the technology of mining and the mechanism of formation of a mining shock, rather than its forecast. The impact hazard of the array during electrometric measurements at the in controlled workings, special measures are taken to identify impact-prone areas of the array.

Theoretical part of the question
However, the iron ore deposits of the Mountain Shoria are represented by a large number of vertical or steeply falling contacts between rocks that compose the array around the mine workings, and the electric profile lines laid along their sides intersect a set of fairly welldefined vertical (steeply falling) rock layers. When an electric current flows or electromagnetic waves propagate through a layered medium, reflection and refraction phenomena are observed at the contacts of the layers, which affects the distribution of the CUES along the measuring profile. Thus, this array should be represented as an alternation of vertical homogeneous isotropic layers of rocks [11][12][13]. If the electrical resistance of the I -th layer is equal to then the entire layered array should be represented as a parallel connection n resistors with resistance Ri each layer. Then the total (equivalent) resistance of the array Requ will be equal to: Subject to (1) formula (2) will take the form: A similar approach to accounting for the number of layers and replacing their set with one equivalent is used in the theory of grounding devices, especially when designing grounding and lightning protection systems.

Results and discussion
Using the formula (3), the electrometric measurements were recalculated for all controlled workings (Cargo and Empty crosscut, South-Eastern field drift) on the horizon (-350). Table  3 shows the results of this recalculation and a comparison of the obtained electrometric coefficients based on the arithmetic mean of the CUES *  K and taking into account the geological structure of the array * *  K .      Table 5 shows that out of 19 measurements, the discrepancy between the electrometric coefficient * *  K and the registered geodynamic phenomena was found in four cases.

Conclusion
Thus, processing of measurement results taking into account the geological structure of electrophiles significantly approximates the electrometric forecast to the real assessment of the seismic events that occurred. The forecast efficiency increases to 80%.