Abstract
Near-fault coal displays some specific structural and textural features. As the distance to the fault diminishes, one can observe ever stronger, gradual degradation of coal, demonstrated by the emergence of structural distortions exogenic in their origin, visible under a microscope. The process of gradual degradation of coal—manifested by the appearance of structural distortions exogenic in their origin—takes place. This can be observed under a microscope. The measurements of the microhardness of structurally altered coal carried out using the Vickers hardness test. For the purpose of this research, a microhardness tester by the CSM Instruments was used. The microhardness of particular structural types of coal was measured. The procedure encompassed both structurally unaltered and altered coal. The tested objects were exogenically fractured fragments, cataclastic, and mylonitic structures. Each of the analyzed structural types displayed a different range of the microhardness, with the highest values confirmed for the structurally unaltered coal. In the case of fractured coal, the microhardness values were somewhat lower. Finally, the lowest values were ascertained for cataclastic coal. Mylonitic coal, in turn, displayed microhardness values similar to those found in the unaltered coal. It was also observed that, in the case of the unaltered, fractured, and cataclastic coal, cracks propagated in the manner typical of brittle materials, whereas the mylonitic coal revealed some degree of elasticity. The analyzed microhardness parameters expose the structural–textural features of coal, particularly when it comes to the degree and character of destruction of the rock’s original matrix. The specific structural–textural composition of particular types of near-fault creations influences both their sorption parameters and the compactness of coal in a seam.
Highlights
In coal, there are always more or less complex systems of fractures, cracks or pores [1,2,3,4]
It is widely believed that almost all gas and rock outbursts occur in areas of tectonic dislocations, as the structurally altered coal that occurs in these areas is “unstable” due to its Energies 2019, 12, 1756; doi:10.3390/en12091756
A sample from the right sidewall of the fault was selected, containing almost 50 percent of structurally altered coal (Table 1); The W3 sample was taken from the “Pniówek” hard coal mine, coal seam no. 403/3
Summary
There are always more or less complex systems of fractures, cracks or pores [1,2,3,4]. It needs to be observed that they may appear in the coal structure as a result of the impact of an increase in the degree of coalification [5], or as a consequence of tectonic distortions affecting a seam [6]. These distortions lead to the appearance of a network of fractures in coal, as well as comminution or even grinding of the coal material [7,8]. Juxtaposing these results with other coal parameters, it will be possible to make predictions as to outburst inclinations of a tectonically distorted seam
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
