Microstructural and thermal properties of coal measure sandstone subjected to high temperatures

Abstract

To study the microscopic structure, thermal and mechanical properties of sandstones under the influence of temperature, coal measure sandstones from Southwest China are adopted as the research object to carry out high-temperature tests at 25 °C–1000 °C. The microscopic images of sandstone after thermal treatment are obtained by means of polarizing microscopy and scanning electron microscopy (SEM). Based on thermogravimetric (TG) analysis and differential scanning calorimetric (DSC) analysis, the model function of coal measure sandstone is explored through thermal analysis kinetics (TAK) theory, and the kinetic parameters of thermal decomposition and the thermal decomposition reaction rate of rock are studied. Through the uniaxial compression experiments, the stress‒strain curves and strength characteristics of sandstone under the influence of temperature are obtained. The results show that the temperature has a significant effect on the microstructure, mineral composition and mechanical properties of sandstone. In particular, when the temperature exceeds 400 °C, the thermal fracture phenomenon of rock is obvious, the activity of activated molecules is significantly enhanced, and the kinetic phenomenon of the thermal decomposition reaction of rock appears rapidly. The mechanical properties of rock are weakened under the influence of rock thermal fracture and mineral thermal decomposition. These research results can provide a reference for the analysis of surrounding rock stability and the control of disasters caused by thermal damage in areas such as underground coal gasification (UCG) channels and rock masses subjected to mine fires.