Underground Coal Mining Significantly Impacts Surface Stability

By Dr. Noopur JainReviewed by Laura ThomsonJan 8 2025

In a recent article in Remote Sensing, researchers investigated the surface multi-hazard effects induced by underground coal mining in mountainous regions, focusing on the relationship between subsidence and various surface hazards.

As mining activities expand, understanding the environmental impacts becomes increasingly critical, particularly in areas characterized by steep topography and geological complexities. The study aims to provide insights into how subsidence affects slope stability and contributes to the occurrence of surface hazards, thereby enhancing the knowledge base for risk assessment and management in mining regions.

Background

Underground coal mining is known to cause significant alterations to the geological and hydrological conditions of the surrounding environment. These changes can lead to surface subsidence, which is the downward movement of the ground surface due to the removal of material from below. In mountainous areas, where the terrain is already unstable, subsidence can be exacerbated, resulting in various hazards such as landslides, sinkholes, and flooding.

The article highlights the importance of monitoring these hazards, particularly in regions where mining activities intersect with natural geological features. Previous studies have documented the impacts of mining on surface stability, but there remains a gap in understanding the specific mechanisms through which subsidence influences the frequency and severity of surface hazards. This research addresses this gap by employing advanced remote sensing techniques and field investigations to analyze the relationship between subsidence and surface hazards in a coal mining area in southwestern China.

The Current Study

The study employed a comprehensive methodological framework that integrated various techniques to assess the subsidence phenomenon and its effects on surface hazards. The research was conducted from March to June 2024, utilizing a DJI MATRICE 300 RTK UAV for high-precision mapping. The UAV was operated at an altitude of 400 meters with a speed of 10 meters per second, ensuring optimal data collection through planned flight paths with 80% longitudinal and 70% lateral overlap. This approach allowed for generating a digital surface model (DSM), orthophotos, and 3D visual models from 1,747 captured images, achieving a resolution of 0.05 meters.

In addition to UAV surveys, the study incorporated InSAR (Interferometric Synthetic Aperture Radar) processing to monitor ground deformation over time. This technique enabled the researchers to analyze subsidence patterns and correlate them with mining activities. Field investigations were also conducted to validate the remote sensing data and gather on-the-ground surface hazard observations. Combining these methods provided a robust dataset for analyzing the cumulative subsidence process and its impact on slope stability.

Results and Discussion

The results of the study revealed a clear correlation between underground mining activities and the occurrence of surface hazards. The analysis of subsidence data indicated that the subsidence process could be divided into three distinct stages: the initial subsidence stage, the accelerative subsidence stage, and the slow residual subsidence stage. Following the commencement of coal extraction, surface subsidence was observed to enter the initial stage almost immediately, although the deformation at this point was relatively minor. As mining progressed, the subsidence accelerated, leading to significant ground movement and increased vulnerability to surface hazards.

The study also documented a notable increase in the frequency of surface hazards in the study area, particularly following heavy rainfall events. The total rainfall from July to September 2023 amounted to 730.5 mm, accounting for 73.1% of the annual total rainfall. This period coincided with six heavy rainfall events, each exceeding 50 mm of daily precipitation. The researchers found subsidence and intense rainfall created conditions conducive to landslides and other surface hazards, particularly near steep slopes with significant topographic variations.

Furthermore, the research highlighted the role of mining in exacerbating these hazards. The presence of mining activities below steep slopes sharply increased the frequency of surface hazards, underscoring the need for effective monitoring and risk management strategies in such environments. The findings contribute to a deeper understanding of the environmental impacts of underground mining, particularly in mountainous regions where the interplay between geological features and human activities can lead to severe consequences.

Conclusion

In conclusion, the study provides valuable insights into the surface multi-hazard effects of underground coal mining in mountainous regions. The research successfully elucidates the relationship between subsidence and surface hazards by employing a combination of UAV surveying, InSAR processing, and field investigations. The findings indicate that underground mining significantly influences surface stability, particularly in steep topography and heavy rainfall.

As mining activities expand, comprehensive monitoring and risk assessment become increasingly critical. This research not only enhances the understanding of mining's environmental impacts but also serves as a foundation for developing effective management strategies to mitigate the risks associated with surface hazards in mountainous regions. The study emphasizes the importance of integrating advanced remote sensing techniques with traditional field investigations to provide a holistic view of the challenges posed by underground mining in complex geological settings.