Impact of petrographic composition on disturbance of coals

Evaluating the disturbance of coal beds is important both in terms of conditions of their working out and in predicting such features as methane capacity, outburst hazard and spontaneous combustion. One of the methods for evaluating coal disturbance is its research using optical microscopy. Coal consists of petrographic microcomponents (macerals) distinguished by optical properties and, most importantly, strength properties. This heterogeneity of the coal matter largely determines the nature of coal disturbance. This paper shows the impact of the macerals of the inertinite and liptinite groups on the development of disjunctive and plicative coal disturbance. The purpose of the paper is to establish the features in the formation of plicative and disjunctive disturbance of coal depending on its petrographic composition. The research is carried out with the help of a video-optical complex: MBI-11, HB 200, and Scope photo software. It is noted that the more diverse the petrographic composition of coals is, the less developed fracturing under equal other conditions coals have. The petrographic composition affects the disturbance of coals not only at the level of lithotypes but also at the level of macerals. Liptinite and inertinite prevent the development of endogenous fracturing. Liptinite and inertinite contribute to the development of exogenous fracturing. An increase in the total density of coal at high stages of metamorphism levels out the effect of the petrographic composition. Coals of low stages of metamorphism are characterized by the greatest diversity of composition. With the growth of metamorphism, the difference in strength and optical properties of the macerals is gradually leveled and coals of the C-coke, F-fat marks (CF) are characterized by the greatest fracturing. To the L mark, the composition becomes even more homogenous (features of vitrinite and liptinite fully become the same) but the overall density of coal increases, and the fracturing decreases. As long as differences remain in the strength properties of macerals (low and middle stages of metamorphism) the presence of liptinite and inertinite prevents the development of fracturing. Examples of suppression of fractures by macrospores and fusinite are given in the form of microphotographs. There are cases of interlayer slipping and slickenlines. The importance of petrographic research in evaluating both rupture and plicative disturbance of coals is emphasized.