Experimental Research on Coal-Gas Outburst Prevention by Injection Liquid Freezing during Uncovering Coal Seam in Rock Crosscut

According to the existing problems of the control measures of uncovering coal seams in rock crosscut, such as long time of uncovering coal, poor construction safety, etc., the main effect factors of coal–gas outburst of uncovering coal seams in rock crosscut are analyzed, the existing hypotheses and the process of coal–gas outburst are described, and then the feasibility of the injection liquid freezing to prevent the coal–gas outburst is analyzed. It is concluded that the measure of the injection liquid freezing has the following functions: ① changing the physical properties of coal, ② improving the integrity of the surrounding rocks of the coal–rock interface, ③ enhancing coal strength, ④ effectively avoiding the discontinuous deformation of coal and rock under the action of gas pressure, ⑤ strengthening the block action of the external coal, ⑥ changing the stress distribution of coal near rock crosscut. The freezing makes the freezing ring in the roadway surroundings become a relatively stable flexible combination, which has a better stability. The experiment device of injection liquid freezing is designed, and the coal samples are analyzed before and after the freezing. The experiment results show that the indexes of coal–gas outburst are greatly dropped after adopting the measure of the injection liquid freezing, which can effectively control the coal–gas outburst. The experiments also show that it is feasible to prevent coal–gas outburst by the technology of the injection liquid freezing. The study results provide a new way to prevent the coal–gas outburst in uncovering coal seams in rock crosscut.