Research on surface deformation law of closed mines based on SBAS-InSAR

After the mine is closed, the coal and rock mass undergoes weathering degradation and strength reduction under the action of various factors such as stress, groundwater and oxygen. Moreover, the stress and bearing capacity of the mining fractured rock mass is changed, which is likely to cause secondary deformation of the surface of the goaf. Most of the existing researches focus on the monitoring of surface deformation during the mining process, while there are few researches on the monitoring of surface deformation after mine closure. To investigate the surface deformation law of closed mines, 62 Sentinel-1A images from 2015-12-21 to 2019-12-24 and small baseline subset-interferometric synthetic aperture radar (SBAS-InSAR) technology are used to obtain the surface deformation results and deformation laws of the time series within 4 years of the closed mines in western Xuzhou (including Pangzhuang Mine, Jiahe Mine and Zhangxiaolou Mine). The research results show that the maximum surface subsidence rate in three mines is -48 mm/a, and the cumulative maximum subsidence in 4 years is 178 mm. The surface of the Jiahe Mine shows subsidence followed by uplift, while the surfaces of the Pangzhuang Mine and Zhangxiaolou Mine continue to sink. The maximum surface deformation of three coal mines within 4 years is 1.70 mm/m, and the maximum curvature deformation is -0.039 mm/m2. Through interpolation statistical calculations, the surface deformations which are greater than 10 mm of Pangzhuang Mine, Jiahe Mine and Zhangxiaolou Mine are 10.5, 13.7 and 11.6 km2 respectively, and they are increasing year by year.