Mechanical Performances and Pore Features of Coal Subjected to Heat Treatment in Approximately Vacuum Environment

Abstract

The physical and mechanical performances of coal, which does not just depend on the initial mineral composition and structure, are also dominated by the later engineering and geology environments, including high temperature, water saturation, and corrosive effect. In this paper, coal specimens, after high temperature treatment in an approximately vacuum environment, were conducted to the uniaxial compression, Brazilian split, scanning electron microscope (SEM) and mercury intrusion tests, respectively, to investigate the influence of temperature on the mechanical behaviors and pore features. The results showed that the mechanical parameters decrease gradually with an increase in temperature, presenting four stages: 25°C–200°C, 200°C–300°C, 300°C–400°C, and greater than 400°C. Increases in temperature also lead to the increase of porosity, together with the transformation of pore diameter, especially at 400°C–450°C because of the seriously thermal cracking and decomposition. Unexpectedly, due to the structure redistribution of mineral grains, from 450°C to 500°C, both the porosity and pore diameter show a drastic drop.