Effect of Methane Adsorption on Mechanical Performance of Coal

Abstract

Understanding the influence of methane adsorption on coal mechanical properties is an important prerequisite for preventing coal mining and gas mining disasters. In the present research, meager coal and gas coal samples were obtained from Huaneng Yunnan Diandong Energy Co., Ltd. The triaxial compression tests were carried out under different methane adsorption equilibrium pressures and confining pressures. The influence laws of different factors on the mechanical properties of coal were analyzed. The results show that the triaxial stress-strain curve of adsorbed methane coal has similar morphology with that of non-adsorbed coal. Under the same confining pressure, the stress-strain curve morphology of coal before and after adsorbing methane is basically the same but the compressive strength of coal after adsorbing methane decreases. The greater the adsorption equilibrium pressure of methane, the smaller the compressive strength of coal. The change in the mechanical properties (compressive strength and elastic modulus) of coal caused by methane adsorption can be described by the Langmuir curve and the correlation coefficient is more than 0.99. Under any stress environment, high-rank coal shows greater strength and lower elastic modulus than low-rank coal, which is mainly due to the existence of a developed cleat system in high-rank coal that provides more conditions for methane adsorption. The research results provide important data-based support for the prevention of coal and gas outbursts.