Goaf-induced deformation along the Chengdu-Kunming high-speed railway and its impact on engineering stability

High-speed railways are highly sensitive to mining-induced subsidence, making the identification of goafs along railway corridors and impact assessment crucial for construction and operation. This study investigates the Weiyuan section of the Chengdu-Kunming High-Speed Railway traversing a low-mountain coal mining area. An integrated approach combining historical data, drilling surveys, InSAR monitoring, and theoretical modeling was used to map mineral resources, mining activities, goafs, and surface deformations. Then, an evaluation framework for assessing the potential impact of goaf on railway engineering stability is established, thereby evaluating the potential threat of goaf. Findings indicate that the overlying thick-bedded sandstone layer (∼129 m) above the goaf significantly mitigates the transmission of deformation from the goaf to the surface. InSAR monitoring spanning from November 2016 to April 2024 reveal that historical mining caused minor subsidence (<10 mm/yr), with current deformation rates generally within ±10 mm/yr. Empirical calculations indicate a safe mining depth threshold of 96 m, while actual depths significantly exceed this value, posing minimal railway risks. By calculating the influence angle of the subsidence basin and analyzing its relationship with the railway alignment, the study identifies that the direct impact of goafs is primarily concentrated in the Bakubutian coal mine areas. Based on these findings, targeted risk mitigation strategies are proposed to ensure the long-term safety and stability of railway engineering. This study provides scientific support for the Chengdu-Kunming Railway’s safety and offers transferable methodologies for railway projects in similar mining-affected regions, emphasizing the importance of integrated geological-engineering assessments in infrastructure planning.