Using time series InSAR to assess the deformation activity of open-pit mine dump site in severe cold area

Purpose There are a large number of open-pit coal mines in the world, and their dependent, heterogeneous dump sites are one of the world's largest chronic waste concerns. The long-term existence of dumps is vulnerable to non-uniform deformation and erosion simultaneously, seriously threatening also the surrounding geological and ecological security. Hence, it is critical to monitor the potential geologic hazards erosion activity of such a large, unstable accumulation. Materials and methods In this study, topographic observations were performed using the Terrain Observation by Progressive Scans (TOPS) mode of the up-to-date high-quality synthetic aperture radar (SAR) images from the Sentinel-1B (S-1B) satellite, while unmanned aerial vehicle (UAV) photogrammetric data were used to assist in phase unwrapping, showing the deformation and soil erosion of the Baorixile open-pit coal mine dump in China from September 2016 to September 2019. At the same time, the possible areas of geological disasters were predicted, and the formation mechanism of different types of erosion was analyzed. Results and discussion The validation indicates that the deformation monitoring results by S-1B data matched well with the measured value. The soil consolidation has a positive effect on improving dump geological stability, while soil erosion has the opposite effect. The high correlation between accumulation consolidation and stacking height was used to distinguish soil consolidation and soil erosion from total deformation. The dump has undergone subsidence and/or erosion under gravity and non-gravity factors. The overall cumulative vertical subsidence and slope deformation ranged from 12 to - 298 mm (negative values indicate that the target moved away from the sensor) and from 4 to 365 mm, respectively. The deformation was aggravated with the increase of the stacking height of the dump site, especially at the edge of the top area. Soil erosion and slope instability were the results of the combined action of multiple factors, such as spring snowmelt erosion, summer (rainy season) surface runoff erosion and internal seepage erosion, autumn wind erosion, and winter frost heaving erosion. Potential slope destabilization hazards and hidden danger areas of slope instability need continuous attention. Conclusion In summary, the deformation analysis suggests that the collaborative application of S-1B SAR image and UAV photogrammetric data demonstrates the practicability of the fine deformation monitoring service in the dump site and can be a useful tool for long-term continuous deformation and soil erosion monitoring.

Automated summary

The study utilized SAR images and UAV data to monitor the topographic changes and soil erosion of an open-pit coal mine dump in China. The results showed a correlation between soil consolidation and dump stability, while soil erosion had a detrimental effect. The research demonstrated the effectiveness of using satellite and UAV technology for continuous monitoring of deformation and erosion in dump sites.