Insight into the mechanical degradation of coal corroded by concentrated brine solution

Underground water reservoirs (UWR) of coal mine plays a significant role in enhancing the ecological environment and safeguarding water resources. The water stored in UWR, known as brine solution, seriously damages the mechanical properties of the coal pillar. However, the mechanical degradation characteristics of coal under the action of different concentration solutions are still unclear. In this paper, we propose a novel coal corrosion device to simulate the real environment, designed to ensure the effective dissolution of the solution to the samples. Here we show the results of brine solution corrosion tests, considering ion composition changes, microscopic CT imaging, and mechanical properties. The solution ion composition experiences significant changes after the corrosion test. The variation in $M{n}^{2+}$ ion content can reflect the reaction degree and trend of water–rock interaction; CT test visually demonstrates the microstructural changes, allowing for direct observation of dissolution, generation, and attachment phenomena. The specimen’s overall porosity increases after corrosion; Triaxial compression tests were conducted, and both solution concentration and corrosion time can cause varying degrees of mechanical parameters degradation. Our results demonstrate how solution concentration affects coal and the extent of its impact. We anticipate our research will contribute to the construction and long-term safety of UWR.