Temperature influence on macro-mechanics parameter of intact coal sample containing original gas from Baijiao Coal Mine in China

Investigation of temperature effect on mechanical parameters of coal is very important for understanding the mechanical response of coal bed at high temperature. It is especially beneficial for mitigating the thermal-induced disasters occurred in those coal mines suffering from heat hazard. In this work, coal samples, obtained from the No. 2442 working face of Baijiao Coal Mine, were subjected to uniaxial compression ranging from 20 to 40 °C with an interval of 5 °C. The apparatus used was designed to obtain deformation of a stressed sample, as well as the emission of gases desorbing from coal matrix. The adsorbed gas desorption caused by heating is measured during the entire testing. It is evident that the concentrations of releasing gas (containing methane, carbon dioxide and ethane) slightly rise with increasing temperature. Gas movement observed is closely related to the deformation of coal sample. Both uniaxial compressive strength and elastic modulus of coal samples tend to reduce with temperature. It reveals that increasing temperature can not only result in thermal expansion of coal, but also lead to desorption of preexisting gas in coal which can in turns harden coal due to shrinks of the coal matrix. Even though desorption of adsorbed gas can contribute to the hardening effect for the heated coal, by comparison to the results, it could be inferred that the softening of coal resulted from thermal expansion still predominates changes in mechanical characters of coal sample with temperature at the range from 20 to 40 °C.