Experimental study on the influence of water–rock interaction on the time-varying characteristics of coal rock mass

In order to study the influence of water–rock interaction on the mass time-varying characteristics of coal rocks, coal was selected as the research object and subjected to chemical immersion tests with different pH aqueous solutions for 12 days. By experiment, the time-varying patterns of mass change fraction in coal samples, pH value in solution, and ions concentration of calcium and magnesium were obtained. Based on the gray correlation theory, the correlation degree between the mass change fraction and four influencing factors was analyzed. The gray prediction models for the mass time-varying characteristics of coal rocks have been established. The research shows that: (1) the influence ways and degree of different pH aqueous solutions on the mass changes of coal rocks are different, (2) during the process of water–rock interaction, the change law of pH value, ions concentration of calcium and magnesium in solution are obvious, (3) the multiple regression models can be used to predict the mass change of coal rocks accurately under water–rock interaction.