Applicability and Feasibility of InSAR-Based Mining Subsidence Monitoring Under Overburden Isolated Grouting Backfill Mining Conditions

With its high spatiotemporal resolution and wide-area coverage, InSAR technology has become an essential tool for monitoring mining-induced surface subsidence. However, the large-gradient deformation caused by the traditional caving method has hindered this technology’s widespread application in subsidence monitoring. With the increasing adoption of backfill mining techniques, both the magnitude and the gradient of surface deformation have been significantly reduced, creating new opportunities for applying InSAR to subsidence monitoring in mining areas. Nevertheless, current research on InSAR under backfill mining conditions remains relatively limited, particularly with respect to the applicability of time-series InSAR techniques in such settings. In this study, the Wu’an mining area, characterized by the traditional caving method, and the Fengfeng mining area, which employs overburden isolated grouting backfill mining, were selected as representative cases. By integrating Small Baseline Subset InSAR (SBAS-InSAR) time-series deformation results with ground-based leveling measurements, we comparatively analyzed the interferometric coherence characteristics and deformation monitoring performance associated with the two mining methods. We then evaluated the monitoring applicability and engineering feasibility of InSAR under overburden isolated grouting backfill mining conditions. The results indicate that, under similar surface land cover conditions, the gradient of surface deformation exerts a strong influence on interferometric coherence. Comparison with leveling measurements shows that the RMSE in the Fengfeng mining area under overburden isolated grouting backfill mining is at least 68.2% lower than that in the Wu’an mining area under caving mining. Moreover, overburden isolated grouting backfill mining can effectively mitigate mining-induced surface deformation, limiting the maximum subsidence in the Fengfeng mining area to less than 300 mm and to less than 200 mm in village areas. Using Sentinel-1 data and a conventional SBAS-InSAR processing workflow, InSAR demonstrates higher reliability and applicability for surface subsidence monitoring in mining areas under overburden isolated grouting backfilling conditions than in those under caving mining conditions. This study aims to provide a useful reference for mining subsidence monitoring based on Sentinel-1 C-band data and a conventional SBAS-InSAR processing workflow.