Abstract
The shotcrete lining in the underground water sumps of the Shen Dong coal mine in western China has been subjected to long-term exposure to harsh environmental conditions, including repeated dry-wet cycles and high salinity. The elevated chloride ion concentration in the mine water exerts a pronounced corrosive effect on the shotcrete. The performance degradation of shotcrete in highly erosive environments has become a technical bottleneck restricting the long-term safety and reliability of shaft and tunnel engineering. This paper takes the shotcrete in the underground water sump of Shigetai Coal Mine in Shendong Mining Area as the research object. Combined with the surrounding environmental conditions, theoretical analysis is carried out, and a diffusion model of moisture and chloride ions is established. The erosion rate of chloride ions is regarded as the evaluation index in coal gangue shotcrete and ordinary shotcrete. Firstly, the COMSOL simulation software is employed to simulate the erosion rate of 40% coal gangue shotcrete under various water-cement ratios. It is concluded that the coal gangue shotcrete has the strongest resistance to chloride ion erosion when the water-cement ratio is 0.4. Secondly, the erosion rates of chloride ions in coal gangue shotcrete and ordinary shotcrete are, respectively, compared under the optimal water-cement ratio. It is ascertained that coal gangue shotcrete has a stronger ability to resist chloride ion erosion under the same water-cement ratio. Finally, the erosion depth of chloride ions in coal gangue shotcrete and ordinary shotcrete is studied through experiments, and the chloride ion concentration on the surface of specimens at different erosion ages. The research finds that the experimental results are basically consistent with the numerical simulation results. The results indicate that coal gangue shotcrete with a 40% replacement rate of coal gangue and a water-cement ratio of 0.4 exhibits the highest resistance to chloride ion penetration. Furthermore, a novel approach is proposed for investigating chloride ion erosion in concrete, which involves establishing a moisture-chloride ion diffusion model and performing numerical simulations. The approach aims to reduce the loss caused by multiple experiments, save experimental costs, and time. It is also proposed to prepare shotcrete with coal gangue to consume a large amount of coal gangue and reduce the discharge of coal gangue, and a new method is provided for the comprehensive utilization of coal-based solid waste.