Monitoring and numerical analysis of slope deformation in a coal mine in the southwest mountainous regions of China

As underground coal mining activities are increasing in the southwestern mountainous areas of China, the geological safety issues related to ground subsidence and slope deformation have emerged as significant concerns. These issues have started to impact the routine mining operations. Monitoring deformation and analyzing the mechanical behavior of mining areas can help reveal the deformation patterns at surface level and on typical slopes in mountainous coalfields, ultimately reducing the risk of landslides. Taking the Guangfeng coal mine as a case study, this paper employs Interferometric Synthetic Aperture Radar (InSAR) and numerical simulation to analyze the influence of surface deformation caused by underground mining activities on slope deformation. The InSAR results indicate the presence of two distinct subsidence areas, labeled as I and II. The maximum annual subsidence rate in area I reaches 72 mm/a, while area II shows an annual deformation rate of 59 mm/a. The subsidence around the mined-out area has triggered sliding deformation in the slopes, which aligns with the numerical simulation results obtained from the fast Lagrangian analysis of continua in three dimensions (FLAC3D). As mining advances further into the working face, greater tensile stress develops at the rear edge of the slope, causing the subsidence at the center of surface which gradually shifts towards the top of the slope. The process of slope deformation related to underground coal mining in mountainous regions can be divided into four stages: the original slope stage, the early stage of underground mining, the evolution stage of composite slope deformation, and the stage of increased surface subsidence in the slope. By combining InSAR technology with FLAC3D numerical simulations, surface movements in mountainous mining areas can be accurately and reliably monitored and analyzed. This approach provides effective guidance for deformation monitoring and prediction of slope stability in mining regions.