Addressing the stability issues of coal mine underground reservoir dams caused by long‐term erosion from highly acidic/alkaline mine water, this study investigates the mechanical property deterioration of fractured coal–rock combined bodies under the action of solutions with different pH values (3, 5, 7, and 9) and immersion times (7–35 days) through laboratory tests. The results indicate that the solution pH shifted sharply towards neutral or weakly alkaline during the initial immersion stage (within 7 days), exhibiting a strong self‐balancing effect. The compressive strength, elastic modulus, and prepeak/postpeak strain energy of the specimens significantly deteriorated with increasing acidity and prolonged immersion time, with the most pronounced effects observed in the strongly acidic (pH = 3) environment. Acoustic emission monitoring showed that the cumulative ring count increased with damage development, further confirming the severe damaging effect of the strong acidic environment on the internal structure of the specimens. Additionally, although the hydrochemical environment influenced the crack development degree in the coal part, all specimens ultimately exhibited a tensile‐shear mixed failure mode dominated by shear. This research reveals the internal mechanism whereby the hydrochemical environment, through the combined effects of chemical corrosion and time, leads to the mechanical property deterioration of coal–rock combined bodies, providing a theoretical basis for the long‐term stability assessment and design of coal mine underground reservoir dams.
Yu et al. (Thu,) studied this question.