Experimental study on the mechanical properties, permeability characteristics, and energy evolution of gas-containing anthracite coal under different loading–unloading speeds

Abstract

In the coal mining process, the stress state of a coal seam will change due to coal-mining-induced unloading, which may lead to the occurrence of coal and gas outburst disasters. According to the change of stress characteristics of the coal seam, the mechanical properties, permeability characteristics, and energy evolution of gas-containing anthracite coal at different loading–unloading speeds were analyzed in this study. The result shows that the strength of anthracite coal samples under different loading–unloading speeds increases with increasing initial hydrostatic pressure and decreases with increasing loading–unloading speeds, presenting the power function relationship. Moreover, the higher loading–unloading accelerated the damage rate of coal samples, resulting in a rapid increase in permeability, which has a significant influence on the emergence of coal and gas outburst. Furthermore, the energy evolution characteristics of coal samples were influenced by the loading–unloading speed, the increase in the loading–unloading speed reduces the total energy, and dissipating energy of the coal sample at the point of failure. The study is of great significance for reducing the occurrence of coal and gas outburst disasters and providing a basis for the design of mine gas drainage.