Corrosion characteristics and dynamic properties of the coal-rock combination under hydrochemical condition

In deep mining and repeated mining of residual coal, hydrochemical field and dynamic load disturbance significantly influence the structure formed by the coal seam and rock strata. This may be unstable and induce dynamic disaster accidents. To study the dynamic characteristics of the coal-rock combination under these conditions, the static test and composition detection were conducted on unsoaked samples. Then, hydrochemical solution with different pH was prepared to conduct the corrosion experiments. Finally, the dynamic compression experiment with the same incident energy was conducted on the corroded samples with the split Hopkinson pressure bar device. The results reveal that the pH value of the solution has obvious self-balance and strong time sensitivity. For the acidic solution, the variation of the apparent characteristics of the samples is mostly obvious. Then, for the alkaline solution, the variation of the samples' apparent characteristics is slightly stronger than that in neutral solution. When the immersing period is equal, the dynamic compressive strength of samples shows the following law: acidic solution <C alkaline solution <C neutral solution <C the state of nature. The sample failure modes are extremely different. The coal is comminuted and the rock is split. With the immersing period increasing, the macroscopic failure characteristics of samples do not change significantly. When the immersing period increases, the dynamic compressive strength of samples in the same solution decreases continuously. The samples in acidic solution have a strong time dependence character. After soaking for 7 days, the decreasing rate is 23. 9%. After soaking for 14 days, the decreasing rate suddenly increases to 55. 3% and, increasing by 31. 4%. After soaking for 28 days, the decreasing rate increases to 67. 4% , slightly increasing by 12. 1%. This study shows that in the production activities of underground deep mining and repeated mining of residual coal resources, more attention should be paid to the serious degradation of the dynamic properties of rock masses, which is induced by the hydrochemical corrosion. © 2023 China University of Mining and Technology. All rights reserved.