Examining subsidence change regularity in high groundwater level coal mining areas using Sentinel-1A time-series data

The high groundwater level coal mining areas have a long history of mining and are mainly located in east-central region of China. Subsidence caused by coal mining occur in several different periods. However, the subsidence change regularity in each periods remains unclear. This study aimed to reveal the subsidence change regularity in high groundwater level coal mining areas during different periods. The Juye coal mine, located in Heze City, Shandong Province, China, was selected for the study. Firstly, 55 Sentinel-1A radar satellite images from August 2018 to July 2020 were acquired for this research. The “two-track method” of D-InSAR technology was employed to process the images. Secondly, based on subsidence velocity of 1.7 mm/day, the subsidence process was divided into three periods: initial, active and weakening. Thirdly, elevation data of ground levelling points were used to check the accuracy of subsidence monitoring using Sentinel-1A data. At last, the subsidence change process in different periods was analyzed and the change regularity was summarized. The results are shown as follows: (1) the monitoring accuracy of different periods is high, and R²range from 0.961 to 0.983. (2) The subsidence characteristics are not obvious in initial period. The subsidence funnel begin to form and the mean maximum subsidence in center is greater than 1400 mm in active period. The subsidence velocity gradually decrease and eventually stabilize in weakening period. (3) Appearance of subsidence, development of subsidence funnels and formation of subsidence basins are spatial period characteristics of coal mining-induced subsidence. The results can provide an important basis for land conservation in mining areas.