Experimental study on pore-fracture evolution law in the thermal damage process of coal

Abstract

High temperature causes thermal damage to coal and alters its physical and mechanical properties. In this paper, in order to study the influence of thermal damage on coal mechanical properties and pore-fracture development, uniaxial compression experiments were performed on coal samples treated under different temperatures. Meanwhile, the evolution law of coal fracture in the heating process was quantitatively studied from macroscopic and microscopic perspectives by using a CT scanning electron microscope (SEM), and evolution characteristics of coal pore structure under high temperature were tested and analyzed. In addition, the influence mechanism of thermal damage to the mine fire was discussed in combination with the characteristics of coal mine fire. The results show that the failure mode of coal sample changes from splitting failure to splitting-tensile combined failure and shear-tensile combined failure with the rise of temperature. As the temperature goes up, the number and length of fractures both grow, while the fracture rate and width increase first and then decrease. The porosity of coal exhibits an upward trend on the whole. Under the action of thermal damage, the internal micropore surfaces of coal become notably rougher. The high temperature thermal damage causes the formation of a loose area at the edge of fire area. This loose area not only affects the fracture field and airflow field of the fire area, but also further induces the fire to spread deeper. The research results can be used as a reference for on-site fire prevention work.