Coal Mining Deformation Monitoring Using SBAS-InSAR and Offset Tracking: A Case Study of Yu County, China

Ground deformation caused by underground coal mining has a large subsidence gradient and high nonlinearity and may cause continuous destruction to the surface structure after mining. A synthetic aperture radar interferometry (InSAR) is a powerful method for measuring and reconstructing the ground displacement. In this article, a total of 19 descending orbit X-band TerraSAR-X and 16 ascending orbit C-band Sentinel-1 images were integrated to monitor the ground displacement of a coal mining area in Yu County (Hebei Province, China) using a small baseline subset (SBAS-InSAR) algorithm. We found that the SBAS-InSAR technology can obtain reliable results in regions without a high gradient deformation by combining the deformation rates derived from both the TerraSAR-X and Sentinel-1 datasets. The maximum subsidence rate was approximately 125 mm/y between 17 June 2015 and 07 January 2016. In the case of large-gradient deformation, it is indeed difficult to obtain the mining-induced surface subsidence information accurately using the conventional multitemporal (MT-InSAR) techniques owing to the limitations of the SAR wavelength. In response to this problem, a new decision-making fusion method based on SBAS-InSAR and offset tracking was developed to monitor the large-gradient settlement in mining areas. The results show that the method developed compensates for the shortcomings of the traditional MT-InSAR technologies in the field of large-gradient deformation and obtains reliable results.