Refined subsidence monitoring and dynamic prediction in narrow and long mining areas based on InSAR and probabilistic integral method

Continuous exploitation in mining areas damages the surrounding environment and has various severe geological impacts. Hence, long-term monitoring of mining areas is crucial to reducing these impacts. Differential interferometric synthetic aperture radar (D-InSAR) is widely applied to monitor the subsidence in mining areas, but it cannot obtain accurate large-gradient subsidence result in the centre of the subsidence basin in mining areas due to the de-coherence phenomenon. The probability integral method (PIM) is a prediction method that can cooperate with D-InSAR (D-InSAR PIM, DPIM) to solve the problem. However, with this method, there is early convergence of the edge subsidence in narrow and long mining areas. Moreover, the PIM can only predict the spatial domain; it cannot achieve dynamic prediction. To address the above problems in the traditional DPIM data processing process, in this study, firstly, the traditional PIM was improved by adjusting the radius of the parameter and constructed an improved DPIM (IDPIM) method. The hybrid algorithm was applied to solve the parameters of the IDPIM method and then acquire subsidence results, thus solving the early convergence of edge subsidence problem characteristic of traditional PIM prediction in mining. Additionally, an area-weighting based fusion method was proposed to integrate the IDPIM results and the D-InSAR results (Area-weighting based fusion of the IDPIM and D-InSAR results, AFID) achieving whole-basin refined subsidence in mining areas. Secondly, based on a summary of subsidence laws in mining areas, the Hossfeld model was introduced and combined with the IDPIM method (IDPIM Hossfeld, IDPIM-H) to construct a subsidence dynamic prediction method. This achieved dynamic prediction of the subsidence in mining areas. A coal mine in Ordos was used as the study area, and the feasibility of the IDPIM method, the AFID method and the DPIM-H method was verified through a comparative analysis of leveling data. The results demonstrated that: (1) The results of the IDPIM method showed 8% and 66% improvement in RMSE along the striking and dip lines, respectively, over the D-InSAR results, improving the early convergence of the DPIM along the dip direction of the mine. (2) The results of the AFID method provide a 69% improvement in whole-basin RMSE over the D-InSAR results, which improves the lack of monitoring capacity in the D-InSAR technology center. (3) The results of the DPIM-H method provide a 35% improvement in basin-wide RMSE over the D-InSAR results, solving the problem of low temporal resolution of the D-InSAR technology and realizing the dynamic prediction with high temporal resolution. These findings provide a theoretical basis for future refined exploration of dynamic subsidence in mining areas