Monitoring and characterization of surface deformation after the closure of coal mines based on small baseline interferometric synthetic aperture radar

Abstract

The surface deformation caused by coalmining generally consists of surface settlement in the mining period and the surface uplift after the closure of the coalmine. This paper attempts to disclose the features of surface deformation after the closure of coalmines in Zibo coalfield. The coalmines in the study area was observed and analyzed in two stages: the mining period and the post-closure period. The spatial distribution and rate of surface deformation were estimated based on the images taken by Envisat's advanced synthetic-aperture radar (ASAR) in the first stage, and based on Sentinel-1A/B images in the second stage. According to the results of small baseline interferometric synthetic aperture radar (SBAS-InSAR), most coalmines in the study area uplifted after closure, and the uplift areas in the second stage basically corresponded to the settlement areas in the first stage. But the uplifts in the settlement basins were more obvious. In the five settlement basins in the south, the uplifts are about 41%, 58%, 34%, 48%, and 35% of the peak settlements, respectively, with an average of 42%. In addition, the time series of surface uplift was not linear, but followed the Richards equation of biological growth. The maximum uplift rate was 170mm/year. The surface uplift is directly caused by the rise of groundwater level, and also affected by local geology. Finally, there is no direct correlation between underground mining location and surface uplift. The research shed new light on the complex surface deformation after the closure of coalmines.