Purpose is to identify behaviour of the graded indices as well as their correspondence to grades, groups, and subgroups of similar coal metamorphic degrees to determine hazardous characteristics of workable beds while mining. Methods. Rank scale and changes in the graded index values help define the coal grades, groups, and subgroups having comparable characteristics as well as ultimate composition of organic mass. Coal ranking involves the intensified metamorphism manifestation in the process of transition from lignite to black coal, and then to anthracite. Findings. Analysis of the total of the fusainized components has shown that coal grading is within less than 10 and more than 69% range. However, in the majority of cases its values are recommended as those being less than 39 or more than 40% which prevents from determination of reliable correlation relationships. Free heaving ratio is considered together with the plastic layer thickness making it possible to determine quantitively only LF, LS, LC, and L grades. In terms of vitrinite response index, being 0.8-1.4%, LS, LC, and L grades may be considered as coal in the central ranking series. The fact supports available changes in the internal structure. Originality. Behaviour of the graded indices of industrial coal-rank classification has been determined to identify hazardous characteristics of workable beds while mining. Practical implications are the possibilities to improve the regulatory system for safe mining of workable beds while determining differences in characteristics of vitrinite coal and fusainized coal.

Purpose is to identify changes in the basic indices of vitrinite reflection as well as content of volatile matter in the process of seam underground transformation influenced by high temperature and pressure and define nature of the changes in the classification indices and their correspondence to grades, groups, and subgroups of similar metamorphic coal transformations to determine hazardous characteristics of seams while mining. Methods. Selection of the most adequate basic index, evaluating metamorphism degree of coal seam and forecasting of their hazardous characteristic demonstration while mining, is based upon the average data of coal composition in Donbas depending upon the stages of seam metamorphism. Findings.Analysis of indices of the current industrial classification and normative base has shown the following. They cannot characterize directly the coal metamorphism connected with changes in composition and properties of the original organic substance. It has been mentioned that volatile matter do not demonstrate specifically ultimate composition of the organic matter and phase coal composition while fluid extraction from seams during their metamorphic transformations. Only the total release of gaseous products without identification of the released gases is defined by its value. Average vitrinite reflection has been defined experimentally along with other indices to identify the coal grades. For that reason, values of the index not always correspond to coal metamorphism degree in their grade ranking. Originality. Nature of changes in the classification indices of industrial coal ranking has been defined to identify hazardous characteristics of coal seams while mining. Practical implications. Possibilities to improve a normative base for safe mining have been defined while determining the classification indices characterizing directly the changes in ultimate composition during metamorphic processes.

Purpose. To improve the regulatory framework for the safe conduct of mining operations, to establish the effect of mineral impurities and moisture on the accuracy of determining the oxygen content, under conditions close to those of coal seams. Methodology is based on the fact that practically for all coal seams of Donbass and the Lvov-Volyn basin indicators of consumer qualities of solid fuels have been established, but they characterize only one organic (combustible) part per dry ash-free state. In this case, the effect of mineral impurities (their content for many reservoirs exceeds 30-40%) and moisture on the change in oxygen content is not taken into account. The manifestation of many hazardous properties of coal seams depends on the ratio of oxygen content with other components of the organic mass and mineral impurities. To bring the quality indicators of coals to a state close to the conditions of mining operations, they were recalculated for each coal seams, taking into account the actual yield of ash and total moisture. Findings. The indicator of the release of volatile substances used in the normative documents for the safe conduct of mining operations for assessing the metamorphic transformations of coal seams does not determine the type of coal by their reduction. Restorability determines the properties of the organic mass based on the ratio of oxygen to its other main components. In addition to the organic mass in the dry ash-free state, the composition of solid fuels includes mineral impurities and moisture. They significantly affect the change in the ratio between the main components. The carbon content in the organic (combustible) mass is more informative in comparison with the yield of volatile substances, an indicator. It functionally controls the sum of the remaining components - hydrogen, nitrogen, sulfur and oxygen. To a lesser extent, but rather high, the closeness of the correlation interdependence was established between the content of oxygen and carbon in the dry ash-free state of the fuel. Such interdependence is completely eliminated when considering the fuel for its working condition, which indicates the random nature of the relationship between the main components of the organic mass and mineral impurities, including moisture, for each considered coal seams. Originality. For the first time, on the basis of statistical processing of experimental data on the quality of coals for almost all coal seams of the Donbass and the Lviv-Volyn basins, the possible limits of the oxygen content for the working state of the fuel were established, which makes it possible to individually consider for each coal seam the ratio between the main components of the organic mass and mineral impurities, including the presence of moisture. Practical implications. The research results make it possible to develop proposals for improving the regulatory framework in terms of predicting the hazardous properties of coal seams during mining operations.

Purpose: to establish a possible correspondence between metamorphic processes with artificial thermal destruction of coals and their ashing in order to identify the components of mineral impurities that can affect the manifestation of the hazardous properties of coal mine seams. Methodology is based on a comparison of metamorphic processes that took place at a certain temperature mode in the bowels of the Earth and the production of artificial coals and their ashing. Results: The research made it possible to reveal the important role of mineral impurities in the formation of the hazardous properties of coal seams. This is due to both the significant possible content of mineral impurities in fossil coals, and the simultaneous presence of the main components that determine the hazardous properties of coal seams (carbon, hydrogen, sulfur, oxygen and moisture), both in the organic and in the mineral parts of fossil coals. To improve the regulatory framework for the safe conduct of mining operations, it is necessary to take into account features of the properties of fossil coals due to the presence of mineral impurities in them. In modern regulatory documents on the safe conduct of mining operations, in general, several indicators are used without proper scientific justification: the mass yield of volatiles during the thermal decomposition of coal, the volumetric yield of volatile substances, the thickness of the plastic layer and the logarithm of the electrical resistivity of anthracites. Their values are related to the dry ash-free mass of organic matter only. This excludes consideration of the influence of mineral impurities on the manifestation of the hazardous properties of coal mine seams during mining operations. In many cases, the content of moisture and sulfur is a criterion for the manifestation of hazardous properties of coal seams. They belong to the integral components of both organic and mineral constituents of fossil coals. The share of mineral impurities in the coals of individual coal seams can be more than 40%. The presence of oxygen, hydrogen, sulfur and moisture in mineral impurities significantly affects the manifestation of the hazardous properties of coal seams during mining. The content of mineral impurities in fossil coals in engineering calculations can be determined on the basis of the ash content of coals according to known empirical relationships, corrected for the content of total sulfur and, in some cases, carbon dioxide. Scientific novelty: the significant influence of mineral impurities in fossil coals on the manifestation of hazardous properties of coal seams during mining operations has been proved. Practical value: the results obtained allow substantiating the methodology for the combined use of the composition of organic and mineral components of fossil coals for a reliable forecast of the manifestation of hazardous properties of coal seams and improving the regulatory framework for their safe mining.

Purpose: to establish the quantitative dependences of gas emissions from the forged coal seam outside the operated areas on the degree of development of treatment works in the mine field. Methodology: the method provides for a comparative analysis of experimental data obtained during the development of several benches in the wing of the minefield. Results: the theoretical model of formation of zones of possible gas evolution from the forged coal seam outside the operated excavation sections at discrete increase of the produced space of the mine field wing by the length of the spent lava is considered. The maximum gas emission both on the excavation site and outside it is associated with the subsidence of the main roof as the development of treatment works and the removal of the treatment face from the split work. Activation of the shift of the counterfeit coal seam outside the excavation section causes an intensive increase in gas evolution, which can significantly exceed its release within the operated excavation section. Such circumstances, to a large extent, affect the safety of mining operations and indicate the need to improve the regulatory framework for the forecast of gas emissions in coal mines. Scientific novelty: statistical processing of experimental data allowed establishing the dependence of the level of gas emissions in mine workings and degassing wells simultaneously from three main factors – coal production and the degree of development of treatment works at the excavation site and within the minefield wing. Practical value: the analysis of long-term experimental results of observations of gas evolution from the forged coal-bearing stratum within the exploited sites and outside them is carried out. With sufficient development of treatment works in the wing of the mine field, the gas emissions outside the operated excavation site can significantly exceed the gas emissions in the site workings and degassing wells.