SCIENTIFIC BASIS FOR THE DEVELOPMENT OF A METHOD FOR FORECASTING THE HAZARDOUS PROPERTIES OF COAL SEAMS

Abstract

Purpose: to develop a method of coal gradation to predict the hazardous properties of coal seams during mining. Methodology: based on the study of the interdependence between indicators of the degree of coal metamorphism, which characterize various aspects of its transformation in geological processes. Results: the dependence of the manifestation of any dangerous property of coal seams during mining operations on the influencing factors of the three blocks is considered. In the general case, the most dangerous properties of coal seams include the release of explosive and flammable gases, sudden emissions of coal and gas, the tendency to spontaneous combustion and the occurrence of endogenous fires, increased dust formation, explosiveness of coal dust and other negative phenomena. To prevent emergencies during mining operations, it is necessary to take into account the influence of factors of all three units. Factors of the first block determine the genetic predisposition of mine shafts to the appearance of dangerous properties under the influence of geological processes and metamorphic transformation of the source material. The factors of the second block include mining and geological conditions of coal seams. On the basis of data on parameters of the first two blocks at stages of designing and operation of the coal enterprise, mining indicators of the third block of factors are put. In contrast to the mining-geological and mining conditions of the second block, the factors of the first block are the least studied and not always reliably established. They must determine under the influence of metamorphism changes in the chemical composition, structure and physical properties of coal in the bowels of the Earth, mainly under the influence of elevated temperature and pressure. Currently, more than thirty factors are known, which in different ways characterise the metamorphic transformations of the starting material. There is a practice when in normative documents for the characteristic of degree of metamorphic transformations of layers in the vast majority of cases one indicator is used – an exit of volatile substances at thermal decomposition of coal without access to air. One indicator can not simultaneously and on all sides characterise the content, structure, chemical and physical and mechanical properties of the organic mass of coal and mineral impurities. It is necessary to proceed from the position that each dangerous property of mine layers depends on a certain influence of several factors of metamorphism. Studies have shown that the carbon content directly controls the overall change in the sum of the main components of organic matter (hydrogen, nitrogen, sulphur, oxygen), and the reflection rate of vitrinite – reflects structural changes in petrographic composition. The chemical activity of coal is also affected by the presence of moisture in different states, composition and properties of mineral impurities. The use of each auxiliary indicator must be justified taking into account the purpose of application and the method of its determination Scientific novelty: the carbon content and the rate of reflection of vitrinite in the range of ranking coal by their degree of metamorphic transformations have a reliable quantitative determination, which allows their use in establishing the hazardous properties of coal seams as the main classification indicators. Practical value: the results obtained allow developing general principles of scientific substantiation of the method of forecasting the dangerous properties of coal seams in combination with mining-geological and mining conditions of work on the basis of carbon content and vitrinite reflection index.