Contortional structures in coal and their effect on the mechanical properties of coal

Abstract

The effect of various tectonical contortional ∗ ∗ They are tectonically developed structures in hand size specimens. features on the mechanical properties of coal has been studied. The hardness of coal from the same seam or same horizon (rank † † Degree of coalification expressed generally in terms of carbon or volatile matter in percentage for dry and mineral matter free sample. ≈ ≈ An isovol is a line containing the points having equal volatile matter. 80–82% of carbon) has been found to decrease in general with the increase in the degree of tectonic intensity. Syngenetically ‡ developed structure is found to retain hardness value identical to that of tectonically unaffected part of the coal. From the known relation between microhardness and rank of coal it appears that tectonically affected part of coal has higher degree of coalification or that tectonically affected coals follow a different microhardness course. Further investigation will be necessary to conclude whether the change in mechanical properties is due to change in the chemical composition, i.e. rank of the coal substance or is as a result of some physical or structural change. The present paper, however, describes mainly different splendid ministructures developed in coal and provides the results of mechanical property tests on different structures for the purpose of scientific correlation.