Justification of the selection of indicators of the degree of coal metamorphism for the prediction of hazardous properties of mine plastics

Abstract

The dependence of the manifestation of any dangerous property of coal mines 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 mines. 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 characterize 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 of air. One indicator can not simultaneously and on all sides characterize 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 and the reflection index of vitrinite in the ranking of coal by their degree of metamorphic transformations have a reliable quantitative definition, which allows their use in establishing the dangerous properties of mines as the main classification indicators. In this case, the carbon content directly controls the overall change in the sum of the main components of the organic mass (hydrogen, nitrogen, sulfur, oxygen), and the reflection index of vitrinite - reflects structural changes in the 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. This allows to develop general principles of scientific substantiation of the method of forecasting dangerous properties of coal mine layers in combination with mining-geological and mining conditions of works on the basis of carbon content and vitrinite reflection index.