STATISTICAL MODELS OF THE CLASSIFICATION INDICATOR OF THE DEGREE OF COAL METAMORPHISM FOR THE FORECAST OF DANGEROUS PROPERTIES OF COAL BEDS

Abstract

Purpose: Based on statistical models of volatile matter yield during thermal decomposition of coal without air access (Vdaf) to establish probable relative errors of its measurement of absolute values which would allow to use the indicator with predetermined accuracy Vdaf as the primary classification criterion metamorphism of coal beds for the prediction of dangerous properties when led mining. Methods. It is used to create several sets of Vdaf values that have some features that are essential for their characteristics, followed by analysis of the statistical characteristics of these sets with the establishment of differences or similarities between statistical models. Results. Six sets of coal beds, which have different features of their creation according to the Vdaf criterion. There were from 114 to 412 variants in each set. As a general conditionally accepted set of 2091 coal beds of different coal deposits. For all (7) sets tested, the hypothesis of a normal distribution of variants according to Pearson’s criterion χ2 was tested. One part of the sets tested was close to the normal distribution of random variables, and the other did not correspond to the normal law. It is established that one of the reasons for the inconsistency of parts of the population with the normal law is the various errors in determining Vdaf depending on the absolute value of this indicator. In addition, individual samples from the conditionally general population have the same nature of the distribution of relative frequencies: with an increase in Vdaf to 10%, they decrease; in the range from 10 to 40% slightly increase; when Vdaf > 40% – again there is a decrease. Based on the close correlation dependences of the relative standard deviations of the volatile matter yield from the averaging curves, the validity of the possible use of Vdaf in engineering calculations of the forecast of dangerous properties of shafts only at its values more than 15-20% is proved. The possible influence of the distance of the coal sampling site to the boundaries of gas weathering zones and geological disturbances, and the high dependence of coal (more than 20%) on the additional error of Vdaf determination was also established. The established possible error values do not guarantee high accuracy of forecasting the dangerous properties of coal beds when using Vdaf as the main indicator of the degree of metamorphism. Improving the regulatory framework for safe mining of coal seams requires justification and application of other indicators of the degree of coal metamorphism. Scientific novelty: For the first time on the basis of statistical models, ambiguous possible errors in determining the yield of volatile substances during thermal decomposition of coal without air access and the inexpediency of its use to predict the hazardous properties of coal beds in mining. Practical significance. The necessity of using other indicators of the degree of metamorphism to improve the regulatory framework for safe mining of coal beds, which directly reflect the content and properties of coal in the process of geological transformations, has been proved.