Effects of high temperature on the microstructure and mechanical behavior of hard coal

Coal is a common porous sedimentary rock whose microstructure and mechanical behavior are often affected by high temperature. In order to deeply investigate the effect of high temperature on the structure and mechanical properties of coal, six groups of coal samples with different heating temperatures were prepared. Various testing methods, including ultrasonic test, scanning electron microscopy, nuclear magnetic resonance and uniaxial compression test, were used in this study. The results showed that the physical and chemical change processes of coal samples under high temperature can be divided into two stages: the stage of drying and degassing and the stage of pyrolysis of the coal matrix. With the increase of heating temperature, the total porosity of coal samples increases, while the integrity and the deformation resistance of coal samples decrease. In addition, the elastic modulus and uniaxial compressive strength of the coal sample decrease with the increase of heating temperature. The Poisson's ratio decreases firstly and then increases with the increase of heating temperature. (C) 2020 Published by Elsevier B.V. on behalf of China University of Mining & Technology.